The Apex Grade Semi Drop-In Threaded Barrel for the Smith & Wesson M&P is available in either a 5.00" or 4.25" option. The stainless steel barrel features a 1:10" twist rate. The design increases accuracy performance making the M&P capable of shooting as small as a 1-1/2 inch grouping at 25 yards. Accuracy test results based on using a mechanical rest. Final results may vary based on shooter ability, ammunition selection and variations in factory firearm tolerances. Barrel is threaded for A 1/2-28", and includes a thread protector. Works with all Smith & Wesson 9mm M&P pistols requiring a 5.00" or 4.25" barrel. Mfg: Apex Tactical Specialties Inc