Metal cased pin wiper seal - for keeping the grease in and the grime out. 
All of our standard seals are made with polyeurethane with a metal exterior,  which makes them both strong and flexible as well as being easy to install. 
If you are looking for a size not listed here, don't stress... Actibush  can source pin seals of almost any size, usually overnight, or we can get them custom made within a few days.