Polymer80 P80G19FSS G19 Gen1-4 Compatible Fluted Barrel 9mm 4.01" Stainless Steel The P80 Line Of G19-Compatible Barrel Is Precision CNC machined From 17-4 Ph Stainless Steel. The Match Grade Drop-In Barrel Is Heat Treated To 42 HRC With 1:16 Rate Of Twist And Is Compatible With Pf-Series Compact Frame And for Glock 19 9mm Gen1-4.