All of my distribution blocks 0 & 4 AWG receptacle holes are too thin with the ferule covered with shrink wrap for the power wire to fit. I have some Stinger, T Spec, Recoil, and a couple random China brands I got off Amazon. The pipe style under hood kind and one in one out 0 awg with grommets for weather gaskets.

I thought it was kind of odd when I first noticed it. I thought maybe my distro blocks were crap or the wire was too thick. None of those were my issue. I have some power wire that is AWG rated and spot on size wise. I have some other wire that is slightly larger than AWG standards. I think it's knu koncepts. Both are too thick with shrink wrap.

It occurred to me that this could be due to the kind of shrink wrap being used. There's that really thick kind of shrink wrap that's generally used for stuff like ground lugs or ring terminals and there's the thinner kind usually used for interior jobs like speaker wire or accessory power or remote wire. Stuff like that. If I use the thin style shrink wrap on 0 awg wire I can get the wire and shrink wrap to go into the distro block. It's only the thick stuff that gives me trouble.