Thanks for your reply Mr. Hitman. I was thinking about getting the Mad bull M4A1 14.5" outer barrel: http://www.madbullairsoft.com/Englis...ge.682x550.jpg
If you look at the link, are those the small grooves that you are referring to (the two small notches that are 35.5mm apart? Thanks!
Originally Posted by Mr.Hitman
Depends on your barrel.. Well if it's an M4 barrel, than the Type B is best, but there might be some modifications needed as the description says on the page of the link.
Also, Type B is more secured, if you got the grooves on your barrel, and it will be already alligned straight. Type A uses nuts to secure onto the barrel.
If you don't want to modify your barrel when Type B doesn't fit, buy the Type A.
Type B will fit if you modify your barrel and make the grooves yourself.