Nitrile
rubber covered oil seals for temperatures up to 110c.
R21/SC (SC usually marked on the seal for single lip) and R23 or TC
(TC also marked on the seal for a twin lip) R23 Oil seals have an extra wiper
(dust lip or twin lip). These seals have rubber Nitrile OD with metal insert,
primary lip and an additional dirt/dust lip (sometimes called a wiper) moulded
with the overall seal width. They can also be referred to as "Semi
dual" lip type, as the name suggests they help prevent the ingress of
dust/dirt into the primary lip area.