Blitzkrieg PTR Front Sight Lock Ring Replacement Lock Ring for Blitzkrieg Components PTR Gen 2 Front Sights. Fits front sights on PTR guns which have a different tolerance than actual HK guns. Made of billet machined 416 stainless steel. These Lock Rings are included with the PTR Front Sights, but can be purchased separately to allow one of our HK Front Sights to fit a PTR gun. This is the only part that is different between our Gen 2 HK and PTR Front Sights. There is a small dimple machined on the side of the part to identify it from the HK lock ring which is shown in the 4th picture. Made in USA