EZ Nuts

[phoque]

M8?

Heser makes those in both M8 and 5/16-18 versions actually. I have other products of theirs like their heavy SS backplate and backup light, very high quality products.

 

[bpodbielski]

Looks like they only have 5/16th right now:

EZ Nutz - Dive Rite | Equipment for Serious Divers

Secure your backplate to a set of doubles, a rebreather, or a single tank adapter with ease using EZ Nutz. Precision-machined from passivated 304 stainless steel, they feature five scalloped edges for a comfortable grip and a counterbored center to reduce galling. Polished and engraved for a...

diverite.com