Posted by Modulus Arms Product Team on 22nd Sep 2024
1/A, 2/B, 3/C, and 4/D Sizing Explained
1/A, 2/B, 3/C, and 4/D Sizing Explained
Modulus Arms has been a leader in 80 lower jig development and router-based tooling since 2014. SpeedMill sizes refer to the four Modulus tooling versions used with Router Jig Extreme products. Standard listings use Version 1 through Version 4. Premium listings use 1A, 2B, 3C, and 4D. Buyers must match the correct size to their router using the compatibility chart on the SpeedMill product page—not by guessing collet size or router brand alone.
Quick answer: there is no universal SpeedMill. Each version corresponds to a router compatibility group on Modulus product pages. If your router requires Version 4 or premium 4D, Modulus also notes that you may need the Large Router Plate for full-size router support.
Why Modulus Uses Multiple SpeedMill Sizes
Handheld routers vary in spindle design, base size, collet interface, and overall form factor. A single generic end-mill solution cannot cover every router model with the same fitment confidence. Modulus addresses that by selling SpeedMill in four versions and instructing buyers to use the published compatibility chart.
That makes SpeedMill sizes a high-intent support query. The searcher usually already owns or plans to buy a router and needs to know which product selector option to choose.
This guide answers that question directly and links to the product page chart, rather than publishing a static router list that can go stale.
[DIAGRAM: Product selector mockup showing Version 1/2/3/4 and Premium 1A/2B/3C/4D with arrow to compatibility chart.]
Standard Version Naming vs Premium 1A/2B/3C/4D
Modulus uses two related naming systems:
| Product context | Size labels shown to buyer |
|---|---|
| Router Jig Extreme SpeedMill | Version 1, Version 2, Version 3, Version 4 |
| Router Jig Extreme Premium Tool Kit with SpeedCoat | Premium SpeedMill 1A, 2B, 3C, 4D |
These labels refer to the same compatibility concept: choose the SpeedMill size that matches your router group. The premium kit adds coated tooling and SpeedCoat language, but the size-selection problem is the same.
Buyers comparing listings should not treat 1A/2B/3C/4D as separate products from Version 1/2/3/4 without checking the selector and compatibility chart. They are premium-size labels within the same router-matching framework.
What Each Size Label Means for Buyers
This guide intentionally does not reproduce the full router chart because product-page charts change and remain the source of truth. Instead, it explains how to use the chart:
| Size label | Buyer interpretation |
|---|---|
| Version 1 / 1A | First router compatibility group on the chart |
| Version 2 / 2B | Second router compatibility group on the chart |
| Version 3 / 3C | Third router compatibility group on the chart |
| Version 4 / 4D | Fourth router compatibility group on the chart; may require Large Router Plate |
The most important support note from Modulus product pages is that routers using Version 4 require the Large Router Plate. Premium kit language also states that routers needing D/4 SpeedMill may need the Large Router Base or Large Router Plate.
That one detail separates useful Modulus content from generic “SpeedMill sizes” pages that never mention full-size router support.
How to Choose the Correct SpeedMill Size
Use this verification workflow:
- Confirm you are buying for Router Jig Extreme or a listed Modulus tooling path.
- Identify your router make and model exactly.
- Open the SpeedMill product page compatibility chart.
- Find your router on the chart.
- Select the matching Version or premium 1A/2B/3C/4D option in the product selector.
- If the chart indicates Version 4 or 4D, check whether the Large Router Plate is required.
- Verify stock status and lead time on the live product page before ordering.
This is a purchasing-support workflow, not an operational guide. It helps buyers avoid the most common compatibility mistake: choosing a SpeedMill size based on router brand alone.
Where Size Selection Appears in Modulus Listings
Buyers encounter SpeedMill size selectors in multiple places:
- Router Jig Extreme SpeedMill
- Router Jig Extreme Tool Kit with SpeedMill
- Router Jig Extreme Premium Tool Kit with SpeedCoat
If a buyer starts with the tool kit rather than the standalone SpeedMill, the size-selection requirement does not disappear. The tool kit page states that the buyer must select the proper SpeedMill version to correspond with the associated router.
That is why this guide links to both the standalone SpeedMill page and the tool-kit category.
Version 3C and the Freedom Jig Router Example
One useful product-page example is the Freedom Jig Router, which Modulus describes as taking a SpeedMill Size 3C. This helps buyers understand that 3C is not abstract labeling—it corresponds to a real router compatibility group.
However, Freedom Jig Router support belongs to the Easy Jig ecosystem. The primary owner for SpeedMill size education remains Router Jig Extreme and the SpeedMill product page.
Common Size-Selection Mistakes
| Mistake | Why it fails | Better approach |
|---|---|---|
| Choosing by router brand only | Multiple models within a brand can map to different versions | Match exact model on chart |
| Assuming any compact router works | Modulus warns against unlisted routers | Use listed compatibility only |
| Ignoring Version 4 plate requirement | Full-size routers may need Large Router Plate | Check plate requirement before checkout |
| Buying replacement end mill first | Replacement assumes existing SpeedMill holder | Confirm base SpeedMill version/path first |
| Confusing premium label with different fitment | 1A/2B/3C/4D still map to router groups | Use chart, not label shape alone |
This mistake table helps buyers avoid the most common size-selection errors.
Premium vs Standard Size Selectors
Buyers sometimes see both Version 1–4 and Premium 1A–4D selectors and assume they indicate different router fitment rules. In practice, they indicate the same compatibility grouping framework applied to different product lines:
| Selector location | Labels shown | Buyer action |
|---|---|---|
| Standard SpeedMill product | Version 1, 2, 3, 4 | Match router to chart |
| Standard tool kit | SpeedMill Version 1–4 | Match router to chart |
| Premium tool kit | Premium SpeedMill 1A, 2B, 3C, 4D | Match router to chart, then decide on SpeedCoat |
The premium path adds coated tooling and SpeedCoat product language. It does not remove the need to verify router compatibility. Always confirm against the chart rather than treating the letter suffix as a separate compatibility system.
FAQ
What do SpeedMill 1A, 2B, 3C, and 4D mean?
They are premium SpeedMill size labels used on Modulus premium tool kit selectors. They correspond to router compatibility groups, similar to Version 1 through Version 4 on standard SpeedMill products.
How do I know which SpeedMill size I need?
Use the compatibility chart on the Router Jig Extreme SpeedMill product page and match your exact router model to the listed version.
Does SpeedMill 4D require extra hardware?
Modulus product pages state that routers using Version 4 or D/4 may require the Large Router Plate. Verify on the current product page before purchasing.
Is Version 3 the same as 3C?
They refer to the same compatibility group in different product selectors—standard Version 3 versus premium 3C labeling. Always confirm against the live chart and selector.
What if my router is not listed?
Modulus advises against using unlisted routers with Router Jig Extreme. Contact support or choose a listed router path instead of selecting a size by guesswork.
Related Resources
- Router Jig Extreme SpeedMill
- Modulus Arms Router Jig Extreme Large Router Plate
- Router Jig Extreme Premium Tool Kit with SpeedCoat
- SpeedMill Explained
- 80 Lower Jig Tool Kits
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