The only thing better than a normal pistol barrel is a threaded pistol barrel. All pistol silencers require one. We noticed a market need for high quality pistol barrels and we stepped in to offer them. Holding to the same commitment to quality as all our products, our threaded barrels are tough enough to hold up under the harshest conditions. Glock 17 TWIST: 1:10 RH THREAD: 1/2 X 28 LENGTH: 5.0a ^2 FINISH:Black Nitride MATERIAL: 416R Stainless Steel Glock 19 TWIST: 1:10 RH THREAD: 1/2 x 28 LENGTH: 4.5" FINISH: Black Nitride MATERIAL: 416R Stainless Steel Glock 21 TWIST: 1:10 RH THREAD: .578 X 28 LENGTH: 5.2a ^2 FINISH: Black Nitride MATERIAL: 416R Stainless Steel