This Lilja Sako Quad 17 HM2 bull barrel is .900" diameter straight. These barrels are true match-grade barrels and made from 1" diameter 416 alloy rifle-barrel-quality stainless steel. Lilja barrels are a true match-grade barrel. When creating barrels, there is only one grade they allow, they best. Made from 1" diameter stainless steel, every barrel, every barrel is created through Lilja's state-of-the-art facility. Lilja replacement barrels do not require any special gunsmithing. Each barrel is cut to a true match chamber. Accuracy with the barrel is excellent. Groups at 50 yards for 5-shots can be expected to be in the .2''s with target ammo. Lilja is synonymous with quality in the barrel replacement industry. Lilja Sako Quad 17HM2 Bull Barrel