The ones from SG are fine. I don't know why they mention that, as some kits don't have these anyway. It's just a section of the tube that is thrown away during a build.Originally Posted by Bradrock
It's not needed anyway.
As long as you have the fcg assembly, stock, dust cover, bolt@handle, mag-well, finger guard, spring with cups, two bushings and a barrel, all is ok.
MK3's are ok, but if I were going to build a semi, I'd go for a mk2, and keep the mk3's for rainy days.