Pretty much all higher end barrels are stock at .689.
The Dye Ultralite and Boomsticks were .689, and that was all you could get. Finally they have other bores, but the DM line of markers and Protos come with a .689. Timmys come with a .689. The All American barrels are .698 that come with the Shocker if I'm not mistaken.
Angels come with a .690 to a .710 step bore that last time I looked, but they are the odd one out.
I used to use all kinds of barrel kits, but now I've just got an Ultralite I use on everything, and unless I'm shooting some oddball huge bore paint (like System-X Steel), I don't have problems.
It's not like FEP is doing anything super oddball here. It takes cocker threads, so just slap on a barrel that you like.