These funnels are machined on CNC equipment. The outside diameter is .498 and the inside diameter is .452. These funnels are for use with the 45 caliber bullets that have been sized to fit in a .450-458 barrel. The bullets must be sized smaller than .452 or they will not pass through the stem.
Machined from either stainless steel or aluminum with several different stem length available to best fit your muzzle brake.