RocknRoller RSHM2 Multi-Media 2-Tier Shelf for Multi Cart (Discontinued) Designed to transform your Rock N Roller cart into a fully functional mobile workstation The large main shelf measures 24 x 36 inches to provide ample work space The Multi-Media shelf fits models R8, R10, R12. Multi-Cart NOT included. The RSHM2 is the multi-cart's shelf attachment only.