Comparison : Item # B4764-01B, 303 Stainless Steel Gasketed Window Sight, Without Reflector, 11/16" Hex, 1/2”-20 Thread with Nut
Item # B4764-02B, 303 Stainless Steel Gasketed Window Sight, Without Reflector, 13/16" Hex, 5/8”-18 Thread with Nut
Item # B4764-03B, 303 Stainless Steel Gasketed Window Sight, Without Reflector, 15/16" Hex, 3/4"-16 Thread with Nut
Item # B4764-04B, 303 Stainless Steel Gasketed Window Sight, Without Reflector, 1 1/4" Hex, 1"-14 Thread with Nut
Item # B4764-05B, 303 Stainless Steel Gasketed Window Sight, Without Reflector, 1 1/2" Hex, 1 1/4"-12 Thread with Nut