This product is either discontinued or we cannot get that from suppliers.
Poly Plantronics Spare 88225-01, Ear cushion, Material Foam, Compatible Poly - Plantronics Blackwire C310, C320.
The Foam Cushions for Blackwire 310/320 USB Headsets from Plantronics, you can replace old and worn out ear cushions to help maintain a maximum level of comfort when using the Blackwire 310 or 320 USB headsets.