When routing your coax through metal or plastic, it is a good idea to use a grommet to prevent sharp edges from tearing or cutting your coaxial cable. 

The CGA package contains 4 grommets (2 for RG-58 and 2 for RG-59). 

Either size requires a 3/8" hole. 

When FireStik installs them, they put two at each hole so if one gets damaged you can cut it off and slip the other into place without the need to reprocess the end of the coax.