M4 Pre-Sized Internal Sleeve Pack

Internal sleeve for the M4 3 Piece collar in pre fit sizes.

-Pre-fit instructions

**Please allow and extra 3-4 business days for processing pre-fit sleeves** All selectable sizes are typically stocked, however we may run out of a certain size due to demand.

If you have access to a micrometer and know how to use it effectively, we offer pre-sized sleeves available in .001″ increments. It is highly encouraged that you use a micrometer rather than calipers for measurement due to their ability to acquire a more precise measurement. To avoid abuse of this system, you will be responsible for return shipping charges if you measure incorrectly.

Sleeves are stocked in sizes from .719-.745″. If you need a size outside that range, contact us with your barrel information and we may be able to help you get one that fits.

Measure the diameter of the barrel immediately ahead of the gas journal. If your measurement is .748″ or larger, you are likely measuring the gas journal itself and need to double check. You also need to measure at least once more near the muzzle. If any point of the barrel is larger than the first measurement, your barrel may require gunsmithing. Taper or steps that are no more than .001″ larger than the first measurement are typically still useable. Some barrels have engraving or roll marks with high spots which may need to be removed with a stone or file. The pre-fit option comes with an additional  +.001″ and a -.001″ sleeve so you have some flexibility in fitment. If your measurement is in-between sizes, round up. While a snug fit is desired, the outer collar may compress even a .002-.003″ larger sleeve enough to prevent movement after installation.