All barrels require minor Gunsmith fitting except for Glock 17 and 22, in which we make both Drop-in and Gunsmith fit.   Detailed Barrel Specifications: Material used is 416R Stainless Steel heat treated to 40 Rockwell C. All barrels are broached and manufactured from bar stock material or forgings, depending on availability. All are guaranteed for accuracy. All barrels are 1 in 16 twists and 6 lands and grooves irrespective of caliber. This is a twist rate that will allow the barrels to shoot a wide variety of bullets with excellent accuracy.   Bores are as follows:  9mm/38 Super . . . . . . . . . . . . 355 to .3555 Groove & .348 Bore.  40 S&W/10mm . . . . . . . . . . . . 400 Groove & .390 Bore  45 ACP . . . . . . . . . . . . . . . . . . . 451 Groove & .442 Bore   Hood and bottom lug is oversized and requires minor fitting. Chambers are cut short and will require correct head spacing after fitting. Fitting instructions are supplied.   Please specify spring weight that you choose to buy under the comments section at checkout