I cleaned the stainless steel hex keys to a Class B UHV Standard (normal cleaning but no bake out. LIGO does an air bakeout for 24 hours but I think this is unnecessary). Class B parts can come into contact with UHV parts but cannot be left in vacuum.

The smallest hex key in this set is 3/32". We need 5/64", 1/16", and 0.050" hex keys. McMaster has some Titanium hex keys. I didn't see any better options.