Image 1: .750 Inter diameter bore, Low-Profile Gas Blocks (Back)

Image 2: Stainless Steel Set Screw Type .750 Diameter Bore  (Back)

Image 3: Stainless Steel Clamp Type .750 Diameter Bore (Back)

Image 4: Steel Set Screw Type .750 Diameter Bore (Back)

Image 5: Steel Clamp Type .750 Diameter Bore  (Back)

Image 6: Two Metal Types and Two Mounting Methods (Back)