List Price: NA Advanced Double Lock Valve locks in air two ways. Four beds in one: 1 & 2 Use separately as two twin beds; 3 Zip together for a king-size bed; or 4 Zip, stack & snap together for a twin double-high. Advanced Double Lock Valve locks in air two waysFour beds in one:1 & 2 Use separately as two twin beds3 Zip together for a king-size bed4 Zip, stack & snap together for a twin double-high Wrap N Roll saves time just roll into attached carrier, tie and transport.