Surefire Scout Light Rear Caps: Which Tailcap Fits Your Build
By Optics Force | Published: 2026-11-02
Category: Product Reviews
Compare Surefire Scout Light rear caps by body size and switching needs, from the M300 tan cap to the M6XX waterproof tailcap and the M640 Dual Fuel Pro.
Quick answer
Choose the M300 rear cap if you run a compact Scout Light and want a tape-switch-ready tailcap with lock-out in desert tan. Choose the M6XX waterproof tailcap for full-size Scout Light bodies that need a sealed replacement rear cap. If you are buying a whole light rather than a cap, the M640 Dual Fuel Scout Light Pro already ships with a Z68 tailcap and 1,500-lumen output.
The cap must match the light body, not just the brand
Surefire Scout Light rear caps are sold as replacement assemblies for specific light families. The M300 rear cap is built for Scout Lights that accept a SureFire tape switch, while the M6XX tailcap is a replacement assembly for the M6XX Scout Light series. Buying by brand alone is not enough; check the light body model before you order.
This matters most when you are repairing a light or converting a push-button tailcap to tape-switch use. A cap that does not match the body thread and contact layout will not seat or switch correctly, and the catalog does not list thread dimensions, so the model family is your safest guide.
Tape switch, lock-out, and what is not in the box
Both replacement caps are designed to attach a SureFire tape switch, but neither includes the ST07 tape switch. If you are building a pressure-pad setup, budget for the switch separately and confirm that your tape switch is the SureFire type the cap expects.
The lock-out feature on both caps prevents accidental activation during transport, storage, or tactical use. That is a practical advantage for a weapon light that rides in a bag or safe, but it also means you need to remember to unlock the cap before you rely on the light.
Waterproofing and finish are separate decisions
The M6XX cap is described as a waterproof tailcap assembly, which suits full-size Scout Light builds that see rain, dust, or hard field use. The M300 cap is described with aerospace-grade aluminum and a MilSpec Type III hard-anodized finish in black or desert tan, so finish matching is part of the decision there.
Do not assume every Scout Light cap shares the same sealing or finish. The catalog lists waterproofing for the M6XX assembly and color options for the M300 cap; if a specification is not listed, treat it as unconfirmed rather than assumed.
Decision rules for choosing a Scout Light rear cap
- Match the cap to your light body first: Use the M300 rear cap only on M300-family Scout Lights and the M6XX tailcap only on M6XX Scout Light bodies. If your body model is not one of these, stop and confirm the correct assembly before ordering. Write down your exact light model before you shop.
- Decide whether you need tape-switch capability: Both replacement caps are designed to attach a SureFire tape switch, but neither includes the ST07. If you want a pressure pad, add the correct SureFire tape switch to your order. A cap alone will not give you a tape-switch setup.
- Choose waterproofing for hard field use: Pick the M6XX waterproof tailcap when your full-size Scout Light sees rain, dust, or rough transport. For compact M300 builds, the M300 cap is the matching option, but waterproofing is not listed in its catalog facts. Do not assume the M300 cap shares the M6XX sealing.
- Match finish to your build: The M300 cap comes in black or desert tan, so choose tan if you are matching a tan build. The M6XX tailcap is listed in black. Order the finish with the rest of your build, not after.
- Buy a complete light if you also need output: If you are not repairing an existing light, the M640 Dual Fuel Scout Light Pro includes a Z68 tailcap and 1,500-lumen Dual Fuel output, so you do not need a separate rear cap. A complete light can be simpler than cap shopping.
Product facts
- Surefire Replacement Scout Light Rear Cap M300 Tan: Replacement Scout Light rear cap assembly for M300 lights, made from aerospace-grade aluminum with MilSpec Type III hard-anodized finish in black or desert tan, and designed to attach a SureFire tape switch without including the ST07. It is the compact-body choice when you want a tape-switch-ready cap with lock-out and a tan finish to match your build.
Surefire Replacement Scout Light Rear Cap M300 Tan - Surefire Rear Cap Waterproof Tailcap for Scout Light® WeaponLights Assembly M6XX: Waterproof replacement rear cap or tailcap assembly for the SureFire M6XX Scout Light series in black, designed for use with a SureFire tape switch but not including the ST07. It fits full-size M6XX bodies and adds a sealed rear cap for field use, but you still need to supply the tape switch.
Surefire Rear Cap Waterproof Tailcap for Scout Light® WeaponLights Assembly M6XX - Surefire M640 6-Volt Dual Fuel Scout Light® Pro w/ Z68 Tailcap 1500 Lumens: M640 6-Volt Dual Fuel Scout Light Pro with Z68 tailcap, 1,200 lumens on 123A batteries or 1,500 lumens with the Dual Fuel setup, and a Low-Profile Mount for MIL-STD-1913 or M-LOK rails. If you need a complete light rather than a cap, this is the option that already includes a Z68 tailcap and rail-mount flexibility.
Who should buy which
Best for
- Owners of M300-family Scout Lights who want a tape-switch-ready rear cap with lock-out and a tan or black finish
- Owners of full-size M6XX Scout Light bodies who need a waterproof replacement rear cap for field use
- Buyers who want a complete Scout Light with a Z68 tailcap and rail-mount flexibility rather than a separate cap
Not for
- Shooters who need a tape switch included in the box; neither replacement cap includes the ST07
- Owners of Scout Light bodies outside the M300 or M6XX families, who should confirm a different assembly
- Buyers who need a complete light but are shopping only for a replacement cap
