JP Recoil Eliminator    AR-15-type rifles    .750 OD    1/2-28 TPI    Matte black/Stainless steel1/2-28 TPI is the industry standard for AR-15-type rifles and also appropriate for custom applications. The .750 outside diameter is designed for standard military contour barrels, but can be tapered down for smaller contours. The JPRE-2 has a final exit hole of .281 and will accommodate bores up to .243/6mm. The final exit hole of the JPRE-2 can be enlarged to accommodate bores up to .358.