Blitzkrieg Components PTR Lock Ring Sight Adapter Black. 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. Specifications for Blitzkrieg Components PTR Lock Ring Sight Adapter: Manufacturer: Blitzkrieg Components Front Sight Color: Black Gun Make: Heckler & Koch Color: Black Fabric/Material: 416 Stainles Steel Front Material: 416 Stainles Steel Gun Type: Rifle Package Contents: Blitzkrieg Components PTR Lock Ring Sight Adapter Blitzkrieg Components HKPTRLR: PTR Lock Ring Sight Adapter Black