White PVC mounting blocks that anchor the forward-seating backrest bar to your seating. Internal depth 5-1/8″ with a 2″ W × 1/2″ H opening; external dimensions 5-1/2″ L × 3-1/2″ W × 1-3/16″ H. Designed to pair with PPI’s white powder-coated forward-seating bar, part number 4470600-P-WHT.