Bowling ball core · Roto Grip

Roto Grip E.T. Core

The core inside the Roto Grip UFO line

An asymmetric core with mid-lane rev-up and high flare, built for medium to heavy oil. Balls with this core are no longer available at BowlersMart.

  • Asymmetric
  • RG 2.520
  • Diff 0.054
  • MB 0.016
Roto Grip E.T. symmetric core shape inside the ball

Specs

RG AT 15 LB

2.520

Mid-lane rev-up

Revs soonerRevs later

62% of the reactive and urethane balls we stock have a lower RG.

DIFFERENTIAL AT 15 LB

0.054

High flare

Less flareMore flare

83% of the reactive and urethane balls we stock have a lower differential.

MASS BIAS AT 15 LB

0.016

Mild asymmetry

MilderStronger

33% of the asymmetric reactive and urethane balls we stock have a lower mass bias.

RG How soon the ball revs up.Differential How much the ball can flare.Mass bias How asymmetric the core is.
Roto Grip E.T. Core specs by ball weight
Weight RG DifferentialDiff Mass biasMB
16 lb 2.520 0.054 0.016
15 lbUsed on this page 2.520 0.054 0.016
14 lb 2.520 0.054 0.016
13 lb 2.570 0.032 0.010
12 lb 2.590 0.029 0.008

Source: Roto Grip published specs, as shown on BowlersMart’s original Roto Grip E.T. core page (2022). RG and differential change with ball weight; use the row for the weight you throw. The highlighted 15 lb row is the one used on this page.

Looking for a ball like your UFO?

Balls with the Roto Grip E.T. Core are no longer available at BowlersMart. These in-stock balls have the closest RG and differential.

Motiv Apex Jackal Bowling Ball

Motiv Apex Jackal

Motiv Propulsion MXV Pearl Reactive

Heavy oil

Sale price $219.95 Regular price $289.95In stock
Hammer Zero Mercy Solid Bowling Ball

Hammer Zero Mercy Solid

Hammer HK22 C2 Solid Reactive

Medium to heavy oil

Sale price $194.95 Regular price $279.95In stock
Roto Grip RST Hyperdrive Pearl Bowling Ball

Roto Grip RST Hyperdrive Pearl

Roto Grip U-R1 Pearl Reactive

Medium to heavy oil

Sale price $169.95 Regular price $289.95In stock
Hammer Fallout Bowling Ball

Hammer Fallout

Hammer HK22 C2 Solid Reactive

Medium to heavy oil

Sale price $169.95 Regular price $269.95In stock
Brunswick Infinity Quest Pearl Bowling Ball

Brunswick Infinity Quest Pearl

Brunswick EVO Pearl HK22C Reactive

Medium to heavy oil

Sale price $169.95 Regular price $269.95In stock
Storm Identity Bowling Ball

Storm Identity

Storm ReX Pearl Reactive

Medium to heavy oil

Sale price $179.95 Regular price $289.95In stock

Balls with the Roto Grip E.T. Core

None of the 4 balls with the Roto Grip E.T. Core are in stock at BowlersMart right now.

Show 4 balls no longer available at BowlersMart
More bowling balls with the Roto Grip E.T. Core
Ball Cover First seen
Roto Grip UFO Bowling Ball Roto Grip MicroTrax-S20 Solid Reactive December 2019
Roto Grip UFO Pearl Overseas Bowling Ball Roto Grip MicroTrax P-20 Pearl Reactive August 2020
Roto Grip UFO 2 Overseas Bowling Ball Roto Grip eTrax Hybrid Reactive November 2020
Roto Grip UFO Alert Bowling Ball Roto Grip eTrax Hybrid Reactive May 2021

Where the Roto Grip E.T. sits

Each dot is a core in balls we stock. Cores close together roll alike; the cover and layout decide the rest.

DV8 Larceny Core, RG 2.471, diff 0.028DV8 Renegade Core, RG 2.499, diff 0.040Track I-Core Gen4, RG 2.480, diff 0.053Brunswick Vintage Light Bulb Low RG Core, RG 2.568, diff 0.032Brunswick Dual Centric Core, RG 2.509, diff 0.047Ebonite Big Time Core, RG 2.500, diff 0.054Hammer Stacked LED Core, RG 2.545, diff 0.047Hammer Vindicator Core, RG 2.474, diff 0.053Radical Vexed Variant Asymmetric Core, RG 2.490, diff 0.045Radical Modified Intel Symmetric Core, RG 2.483, diff 0.032Motiv Affliction V2 Core, RG 2.480, diff 0.055900 Global Conduit A.I. Core, RG 2.590, diff 0.050Roto Grip GEM A.I. Core, RG 2.490, diff 0.057Hammer Obsession Tour, RG 2.469, diff 0.034Hammer Gas Mask Core, RG 2.500, diff 0.058Ebonite Turbo Core, RG 2.510, diff 0.040Ebonite Centrex Symmetrical Mass Bias, RG 2.460, diff 0.056Motiv Excel Core, RG 2.550, diff 0.030Motiv Detonator Core, RG 2.470, diff 0.055Storm Solarion AI Core, RG 2.480, diff 0.054SWAG Insanity Symmetric Core, RG 2.520, diff 0.034SWAG Fusion Symmetric Core, RG 2.540, diff 0.036SWAG Watcher Symmetric Core, RG 2.510, diff 0.048SWAG Dragon Asymmetric Core, RG 2.480, diff 0.054SWAG Executioner Asymmetric Core, RG 2.500, diff 0.051Motiv Predator V2 Core, RG 2.470, diff 0.054Storm C3 Centripetal Control Core, RG 2.490, diff 0.029Roto Grip Rondure MaxD Core, RG 2.500, diff 0.058Hammer Vibe Core, RG 2.510, diff 0.042Brunswick Alert Core, RG 2.478, diff 0.037Brunswick Rampart Core, RG 2.502, diff 0.051DV8 Collision Core, RG 2.462, diff 0.052Track MC2 Asym Core, RG 2.470, diff 0.046Radical Evil Eye Symmetric Core, RG 2.490, diff 0.046Ebonite Iron Fist V2 Core, RG 2.470, diff 0.053Radical No Doubt Symmetric Core, RG 2.480, diff 0.051Storm Surge Core, RG 2.580, diff 0.024Roto Grip Hyped UP Core, RG 2.500, diff 0.042Roto Grip Morph-Wing Core, RG 2.510, diff 0.051Brunswick Fury Core, RG 2.524, diff 0.038Motiv Sigma Core, RG 2.470, diff 0.047Roto Grip Hustle Core, RG 2.530, diff 0.030900 Global Blast AI Core, RG 2.470, diff 0.055900 Global Strobe AI Core, RG 2.510, diff 0.052Radical Guru Core, RG 2.500, diff 0.044Track I-CORE 3.0, RG 2.480, diff 0.056DV8 Unholy Core, RG 2.500, diff 0.051Storm Catalyst Core, RG 2.500, diff 0.052Hammer Gauntlet Core, RG 2.501, diff 0.050Hammer Raw Hammer Core, RG 2.537, diff 0.038Storm Atmos A.I. Core, RG 2.530, diff 0.042Storm Booster Core, RG 2.540, diff 0.046Track Shuttle Core, RG 2.490, diff 0.038Brunswick Light Bulb Core, RG 2.524, diff 0.030Radical Sneak Attack Core, RG 2.540, diff 0.036Motiv Gear Core, RG 2.480, diff 0.034Hammer Huntsman Core, RG 2.470, diff 0.050Hammer Super LED Core, RG 2.632, diff 0.034Ebonite Enhanced V2 Core, RG 2.480, diff 0.048DV8 Dualistic Core, RG 2.490, diff 0.045Radical Vexed Asymmetric Core, RG 2.490, diff 0.036Motiv Quadfire Core, RG 2.550, diff 0.043Track Stealth Core, RG 2.480, diff 0.056Brunswick Tiered Hexagon Core, RG 2.540, diff 0.045Columbia 300 Piranha Core, RG 2.550, diff 0.043Storm Torsion AI Core, RG 2.470, diff 0.050Storm Element Max AI Core, RG 2.470, diff 0.055Storm Radius Core, RG 2.610, diff 0.020Roto Grip Rondure Tour X Core, RG 2.480, diff 0.034SWAG Unreal Core, RG 2.510, diff 0.047SWAG Craze Core, RG 2.520, diff 0.030SWAG Serpent Asymmetric Core, RG 2.510, diff 0.048Radical Torpedo Asymmetric Core, RG 2.480, diff 0.054Motiv Overload, RG 2.480, diff 0.050DV8 Duality Core, RG 2.480, diff 0.036Hammer Spheroid Core, RG 2.480, diff 0.048Radical Outer Limits Asymmetric, RG 2.490, diff 0.051Brunswick Danger Zone Core, RG 2.501, diff 0.048Storm RAD-TQ Core, RG 2.560, diff 0.051Storm Velocity Core, RG 2.480, diff 0.051Hammer LED Resin Bowling Ball Core, RG 2.586, diff 0.027Epic Spark Core, RG 2.540, diff 0.049Motiv Hadron Dual Density Core, RG 2.500, diff 0.045Track Criterion ID Core, RG 2.490, diff 0.047Brunswick Zone Asymmetric Core, RG 2.478, diff 0.048Ebonite Entity Core, RG 2.510, diff 0.052Roto Grip Rocker AI Core, RG 2.480, diff 0.050Motiv Flux Core, RG 2.570, diff 0.015DV8 Mantra Core, RG 2.490, diff 0.047Hammer Gas Mask Low Diff Core, RG 2.500, diff 0.034Motiv Impulse V2 Core, RG 2.550, diff 0.050SWAG APX V1 Core, RG 2.500, diff 0.042SWAG Fusion Core, RG 2.540, diff 0.036SWAG Judge Core, RG 2.490, diff 0.052900 Global Magna AI Core, RG 2.490, diff 0.044Roto Grip Rondure Core, RG 2.490, diff 0.052Columbia 300 Pulse PowerCOR, RG 2.460, diff 0.045Storm Element Tour A.I. Core, RG 2.470, diff 0.035KR Strikeforce KR Launch Core, RG 2.530, diff 0.047900 Global Ellipse Asymmetric A.I. Core, RG 2.480, diff 0.050Motiv Halogen Core, RG 2.550, diff 0.037Storm C3 + AI Core, RG 2.480, diff 0.031Motiv Gear APG, RG 2.470, diff 0.036Radical Snapshot Symmetric Core, RG 2.520, diff 0.050Hammer High Rev Offset Core, RG 2.489, diff 0.053Hammer Huntsman Tour Core, RG 2.472, diff 0.036Hammer LED Core, RG 2.650, diff 0.015Storm Inverted Fe2 Core, RG 2.570, diff 0.046Storm Capacitor Core, RG 2.570, diff 0.022Storm Velocity A.I. Core, RG 2.470, diff 0.053Storm Atomic Core, RG 2.480, diff 0.053Storm RAD-X Asymmetric, RG 2.480, diff 0.054Storm ID AI Core, RG 2.510, diff 0.055Hammer FAB Asymmetric, RG 2.550, diff 0.051Columbia 300 Shifter Core, RG 2.470, diff 0.050Radical Modified Intel Symmetric, RG 2.480, diff 0.032Columbia 300 Columbia Ricochet Core, RG 2.480, diff 0.054Roto Grip Defense AI Core, RG 2.490, diff 0.053Storm Supercoil Core, RG 2.470, diff 0.053Storm Centripetal HD A.I. Core, RG 2.460, diff 0.056Hammer Modified Infamous Core, RG 2.567, diff 0.049Brunswick Ethos Core, RG 2.480, diff 0.053Hammer Hazmat Core, RG 2.470, diff 0.055Track Criterion MD Core, RG 2.500, diff 0.052Storm Ignition Core, RG 2.490, diff 0.052Roto Grip Momentous A.I. Core, RG 2.480, diff 0.049Brunswick Portal X Core, RG 2.473, diff 0.054Ebonite Emerge Core, RG 2.510, diff 0.053Radical Katana Core, RG 2.500, diff 0.050900 Global Meditate LD Symmetric Core, RG 2.560, diff 0.027Motiv Apex Predator Core (pictured: Motiv Apex Jackal Bowling Ball)1Roto Grip RST Core + AI (pictured: Roto Grip RST Hyperdrive Bowling Ball)2Hammer Super Offset Core (pictured: Hammer Zero Mercy Solid Bowling Ball)3Hammer Aftermath Core (pictured: Hammer Fallout Bowling Ball)4Brunswick Infinity Core (pictured: Brunswick Infinity Quest Bowling Ball)5Columbia 300 Movement Core (pictured: Columbia 300 Command Solid Bowling Ball)6Roto Grip E.T. Core (pictured: Roto Grip UFO Alert Bowling Ball)EARLY REV-UPMID-LANELATER REV-UPHIGH FLAREMEDIUMLOW FLARE2.442.482.522.562.602.642.680.0100.0200.0300.0400.0500.060RG at 15 lbDifferential at 15 lb← Revs up soonerRevs up later →More flare ↑Less flare ↓

Nearest cores, zoomed in

Hover or tap a dot for that core’s numbers. Click a dot to open its page. Drag to move around when zoomed in. The same RG and differential do not guarantee the same ball motion.

This core 1 Nearest cores Other cores

Nearest cores to the Roto Grip E.T. Core
Core Brand Shape RG Diff vs this core
Motiv Apex Jackal Bowling Ball1Motiv Apex Predator CorePictured: Motiv Apex Jackal
 Motiv Asymmetric 2.520 0.055 RG 0.000 · Diff +0.001
Roto Grip RST Hyperdrive Bowling Ball2Roto Grip RST Core + AIPictured: Roto Grip RST Hyperdrive
 Roto Grip Asymmetric 2.520 0.055 RG 0.000 · Diff +0.001
Hammer Zero Mercy Solid Bowling Ball3Hammer Super Offset CorePictured: Hammer Zero Mercy Solid
 Hammer Asymmetric 2.524 0.053 RG +0.004 · Diff −0.001
Hammer Fallout Bowling Ball4Hammer Aftermath CorePictured: Hammer Fallout
 Hammer Symmetric 2.520 0.052 RG 0.000 · Diff −0.002
Brunswick Infinity Quest Bowling Ball5Brunswick Infinity CorePictured: Brunswick Infinity Quest
 Brunswick Asymmetric 2.521 0.051 RG +0.001 · Diff −0.003
Columbia 300 Command Solid Bowling Ball6Columbia 300 Movement CorePictured: Columbia 300 Command Solid
 Columbia 300 Asymmetric 2.510 0.053 RG −0.010 · Diff −0.001

Matches use 15 lb RG and differential.

Drilling and tools

Drilling layoutsLayout guides for symmetric and asymmetric ballsDual angle converterTurn a pin to PAP layout into a dual angle layout

E.T. Core = Equalizer Technology Core… This space aged creation was developed with built in cavities to emulate the use of an extra hole since as of August 2020 the USBC deems them illegal. The built in "Equalizer Cavities" will help increase midlane motion and continuation down lane.  

From Roto Grip’s description

Questions bowlers ask

What is the RG of the Roto Grip E.T. Core?

At 15 lb the Roto Grip E.T. Core has an RG of 2.520. It ranges from 2.520 to 2.590 across the listed weights.

What is the 14 lb RG of the Roto Grip E.T. Core?

At 14 lb the RG is 2.520.

What is the differential of the Roto Grip E.T. Core?

At 15 lb the differential is 0.054. The mass bias is 0.016.

Which bowling balls use the Roto Grip E.T. Core?

Roto Grip UFO Bowling Ball, Roto Grip UFO Pearl Overseas Bowling Ball, Roto Grip UFO 2 Overseas Bowling Ball, Roto Grip UFO Alert Bowling Ball. 0 are in stock now.

Can I still buy a ball with the Roto Grip E.T. Core?

Balls with this core are currently unavailable at BowlersMart. Closest in-stock alternatives by RG and differential include Motiv Apex Jackal Bowling Ball, Hammer Zero Mercy Solid Bowling Ball, Roto Grip RST Hyperdrive Pearl Bowling Ball, Hammer Fallout Bowling Ball, Brunswick Infinity Quest Pearl Bowling Ball, Storm Identity Bowling Ball.

How do the Roto Grip E.T. Core specs change by weight?

At 16 lb: RG 2.520, differential 0.054, mass bias 0.016. At 12 lb: RG 2.590, differential 0.029, mass bias 0.008.

How does the Roto Grip E.T. Core compare with my ball?

Type the ball you throw into the Compare with your ball box on this page. It shows the RG and differential side by side and saves your bag for every core page.

Sources and method

Specs. Roto Grip published specs, as shown on BowlersMart’s original Roto Grip E.T. core page (2022), as published by the manufacturer.

Baseline. The baseline is 265 in-stock, published reactive and urethane balls. Plastic and polyester covers, 2-piece, 3-piece and pancake cores, missing covers and missing RG or differential values are excluded.

Percentiles. Percentiles are the share of baseline balls with a strictly lower or higher value; ties are not counted.

Nearest cores. Nearest cores are ranked by distance on standardized 15 lb RG and differential, with the same symmetric or asymmetric shape preferred among near ties (distance bands of 0.1).

Mass bias. Mass bias is compared among asymmetric balls with numeric mass bias only.

Updated. Catalog and page updated 2026-10-16.

Next lesson

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