The SCS bearing housing is used with LM linear bearings. There are two grooves in the housing for installing retaining rings DIN 472. The archive file contains housings of the following sizes: SCS8; SCS10; SCS12; SCS13; SCS16; SCS20; SCS25; SCS30; SCS35; SCS40; SCS50. The price is for the set, if you need a specific size, write, I will be happy to help.