X-Lite X803/ULTRA/RS ULTRA Cheek Pads  £69.99

Xlite X 803 Cheek Pads

the size options are listed as follows 

the shell size the cheek pad will fit (Shell XXS, XS, S) followed by the actual size of the cheek pad (42mm) followed by what shell size the cheek pad comes in as standard (Std - S)