You get 2 plastic runners that fit into the Ryobi RTS21 5/8” wide inverted T slot. 

These are 5/8" wide.

These fit a Ryobi RTS21 ONLY!

These have been made for this table saw, so they fit well.

The plastic runners do have 3 countersunk holes so you can easily attach these drill to a flat piece of wood to make a crosscut sled for your table saw. Or you can make any specialty jig for your table saw.