The JBL VT4881-ACC Accessory Kit for VT4881 Subwoofers includes everything you need for proper transporting and protection. Included in this accessory kit are a VT4881-DOLLY and a VT4881-COVER. .The dolly is engineered to stack in multiples for easy system handling when you need portable subwoofers. The cover protects your subwoofer and makes it easier to haul if you’re on the go.