These are knurled right hand thread alloy barrel thread cap protectors. 1) 1/2”x20 black 2) 1/2"x20 silver diameter; .980" (24.9mm) deep; 12.05mm 3) 1/2"x20 black diameter 19.4mm x 14.9mm deep 4) 1/2x28 black diameter 19.1mm x 14.9mm deep 5) 5/8x24 black diameter 24.33mm x 14.9mm deep 6) 14x1 Right Hand thread black diameter 18mm x 11.95mm deep 7) 14x1 Left Hand thread black diameter 18mm x 11.95mm deep Select which one you want #1 or #2 or #3 or #4 or #5 or #6 or #7