There are so many different sizes, is the best material to get stainless steel? For example of the rollerchain4less website it states #25, #35, etc
All I can make out on the ones I use is; TSUBAKI R840. I get mine from work. They are used on ratchet cutters we use to cut powerline conducter with.
I use a standard #40 chain master link. It fits three keys, a Sliver Gripper, and a Pocket Tool X (now Leatherman) Brewzer with some super thin washers to keep it all tight.