# 9.3.4 Insert OD chart — standard insert sizes by brand

# Insert OD chart — standard insert sizes by brand

<span style="font-family: monospace; color: #6b7280;">9.3.4</span> <span style="border: 1px solid #d1d5db; color: #4b5563; padding: 2px 8px; border-radius: 3px; font-size: 0.85em;">reference</span>

Finger inserts add a consistent, replaceable grip surface inside drilled finger holes and are used by the majority of fingertip bowlers. Each insert brand and model has a defined **outer diameter (OD)** — the dimension that determines how large the hole needs to be drilled to accept the insert. Drilling to the wrong OD produces a hole that is either too tight (the insert cannot seat) or too loose (the insert spins or falls out). This chart provides standard insert OD values by brand as a quick reference for the hole size field on the spec sheet.

**⚠️ Verify with Spectre team and insert manufacturers:** Insert OD specifications change when manufacturers update product lines. Verify all values in this chart against current manufacturer documentation before publishing, and establish a review schedule to keep the chart current. The values below represent commonly used sizes at the time of writing and should be treated as a starting reference, not a definitive specification.

## 📋 How to Use This Chart

Find the insert brand and model being used. The OD value in the chart is the hole diameter to drill — enter this value as the **finger hole size** on the spec sheet. The insert will seat at this diameter; the bowler's finger then fits inside the insert according to the insert's inner diameter (ID), which is sized separately by the fitter from the bowler's finger measurement.

- ✅ The **hole size field** on the spec sheet should reflect the **insert OD**, not the bowler's finger measurement directly.
- ✅ The bowler's finger size determines which **insert ID** to select — the insert OD determines the hole to drill.
- ✅ When in doubt, verify the OD with the physical insert using a micrometer or caliper before drilling — manufacturer tolerances vary and individual inserts occasionally fall outside the stated specification.

## 📊 Standard Insert OD by Brand

### Turbo

<table id="bkmrk-insert-model-outer-d"><thead><tr><th>Insert model</th><th>Outer diameter (OD)</th><th>Notes</th></tr></thead><tbody><tr><td>Turbo Quad</td><td>`1"`</td><td>Most common Turbo insert. Standard hole size for the majority of fingertip fits using Turbo grips.</td></tr><tr><td>Turbo Quad Jr.</td><td>`29/32"`</td><td>Smaller OD version for junior or smaller-handed bowlers.</td></tr><tr><td>Turbo Switch Grip</td><td>`1"`</td><td>Same OD as standard Quad — designed for quick change between inserts without redrilling.</td></tr><tr><td>Turbo Oval Quad</td><td>Varies by size</td><td>Oval inserts — verify OD with the specific insert before drilling. Oval OD is measured at the widest point.</td></tr></tbody></table>

### Vise

<table id="bkmrk-insert-model-outer-d-1"><thead><tr><th>Insert model</th><th>Outer diameter (OD)</th><th>Notes</th></tr></thead><tbody><tr><td>Vise IT Insert</td><td>`1"`</td><td>Standard Vise insert. 1" OD is consistent across the IT line.</td></tr><tr><td>Vise Oval IT Insert</td><td>Varies by oval size</td><td>Oval inserts — measure the specific insert. Round dimension is typically `1"`; oval adds length in one axis.</td></tr><tr><td>Vise Grip Tape (in-hole)</td><td>N/A — tape applied inside hole</td><td>Grip tape is applied inside an existing hole and does not change the drilled OD. No hole size change required.</td></tr></tbody></table>

### Ebonite / Storm / Roto Grip (shared insert line)

<table id="bkmrk-insert-model-outer-d-2"><thead><tr><th>Insert model</th><th>Outer diameter (OD)</th><th>Notes</th></tr></thead><tbody><tr><td>Standard fingertip insert</td><td>`1"`</td><td>Shared across several brands in the same manufacturing group. Confirm with the specific insert packaging.</td></tr><tr><td>Small fingertip insert</td><td>`29/32"`</td><td>For smaller holes — junior and small-handed bowlers.</td></tr></tbody></table>

### Brunswick

<table id="bkmrk-insert-model-outer-d-3"><thead><tr><th>Insert model</th><th>Outer diameter (OD)</th><th>Notes</th></tr></thead><tbody><tr><td>Brunswick Finger Insert</td><td>`1"`</td><td>Standard 1" OD. Confirm with physical insert — Brunswick has produced inserts at slightly varying ODs across different product generations.</td></tr></tbody></table>

### Master Industries

<table id="bkmrk-insert-model-outer-d-4"><thead><tr><th>Insert model</th><th>Outer diameter (OD)</th><th>Notes</th></tr></thead><tbody><tr><td>Master Finger Insert</td><td>`1"`</td><td>Standard OD. Verify with physical insert before drilling.</td></tr><tr><td>Master Oval Insert</td><td>Varies by oval size</td><td>Measure individual insert — round dimension typically `1"`.</td></tr></tbody></table>

## 📐 OD Tolerance — Why Measuring the Physical Insert Matters

Manufacturer OD specifications are nominal values — the actual insert may be slightly larger or smaller due to manufacturing tolerance. For most inserts the variance is negligible, but for a small number of older, overstocked, or off-brand inserts, tolerance differences can affect seating. A micrometer or caliper reading of the actual insert is the most reliable input for the hole size field, particularly when:

- ✅ The insert is from a brand not listed in this chart.
- ✅ The insert is from an older product line whose specifications may have changed.
- ✅ The bowler supplies their own inserts rather than using shop stock — unbranded or import inserts vary widely.
- ✅ A previous drilling using the same nominal OD resulted in an insert that was too tight or too loose.

## ⚖️ Fit Allowance — Drilling Slightly Larger Than OD

In practice, most pro shop operators drill the hole to a diameter slightly larger than the nominal insert OD — typically `1/64"` to `1/32"` over — to allow the insert to seat cleanly without forcing. The exact allowance depends on:

- ✅ **Ball coverstock hardness** — harder coverstocks compress less around the insert and may need a slightly larger allowance for clean seating.
- ✅ **Insert material** — softer inserts compress slightly on insertion; harder inserts do not. A softer insert may need less allowance than the nominal OD suggests.
- ✅ **Shop standard** — most experienced operators develop a consistent allowance over time. Enter this in the hole size field rather than the bare nominal OD if your shop applies a standard allowance.

**📌 Note:** Enter the **actual hole size drilled** on the spec sheet — including any fit allowance — rather than the nominal insert OD. The spec sheet should reflect what was physically drilled, not the theoretical specification. A future re-drill based on the spec sheet will produce the same result only if the recorded hole size matches what was actually in the ball.

## 🔌 Recording Inserts in Spectre Cloud

Spectre Cloud's spec sheet hole size field accepts the drilled diameter directly. Beyond the hole size, insert details worth capturing elsewhere in the record include:

- ✅ **Insert brand and model** — record in the spec sheet Notes field. A future re-drill can replicate the same insert if this information is on file.
- ✅ **Insert colour** — optional but useful for bowlers who have colour preferences or who use colour to identify their ball in a bag.
- ✅ **Insert OD as measured** — if you measured the actual insert with a caliper and it differed from the nominal value, note both in the spec sheet notes: `Turbo Quad nominal 1" — measured 63/64" — drilled 63/64"`.
- ✅ **Arsenal entry notes** — for Arsenal Plus users, the insert brand and model can also be recorded in the ball's Arsenal entry notes for quick reference when the bowler returns for a re-drill or insert replacement.

## 🎳 Oval Inserts — Additional Considerations

Oval inserts require the hole to be drilled to the insert's oval dimensions rather than a simple round diameter. The hole must match both the round dimension and the oval extension of the insert:

- ✅ Measure the oval insert at its widest point (the oval axis) and at its round dimension before drilling.
- ✅ Confirm the oval orientation on the insert matches the oval cut direction configured in Spectre Cloud — an oval insert seated in the wrong orientation defeats the purpose of the oval cut.
- ✅ Record both the round and oval dimensions in the spec sheet hole size and oval fields respectively — do not record only the round dimension for an oval insert.
- ✅ For oval inserts where the OD varies by insert size, confirm the specific model's dimensions from the manufacturer's current product documentation rather than relying on this chart.

### Related Sections

- 9.3.1 — Pitch suggestion chart (flexibility vs. forward pitch)
- 9.3.2 — CLT chart (lateral tilt angle vs. lateral pitch)
- 9.3.3 — 5/16 rule ring finger span distance chart
- 6.1.3 — Step 3: Set grip type and enter finger measurements
- 7.1.3 — Hole Depth option — setting desired depth for each hole
- 04.x — Spec Sheets: field reference and measurement guide

**✨ Tip:** Keep a physical sample of each insert brand and model your shop stocks, mounted on a card with the OD written beside it, at the fitting counter. When a bowler brings in their own inserts or requests a specific brand, you can confirm the OD visually in seconds rather than searching through packaging or charts. A five-minute investment in a sample card at setup saves repeated lookups across hundreds of fittings.