On the 800H buttons (use the NEMA 4 versions, 800T are indoor), you can get various button covers. The material you use depends on the environment, any chemical exposures etc. I liked using the EPR (Ethylene Propylene Rubber) versions, they are impervious to just about everything you can throw at them, and remain very flexible in extreme cold. I did a lot of work at a sausage packing plant where they were mixing a lot of spices into the meat, and many spices are highly corrosive. The EPR boots were the only ones that lasted a long time, plus it would get very very cold in there, and they didn't get stiff.
But if they are outdoors, then go with the Silicon boots, they don't break down from UV exposure. The standard boots that come on the 800H are made of Chlorosulinated Polypropylene and are pretty good all around, but they tend to get a little stiff in extreme cold.