It really comes down to the wire… literally. Both a King and a Split King are two pieces joined together with a clamp. It just depends on whether you plan on using a single King mattress or two Twin XL mattresses on your base. If you’re using a King Mattress: Simply join the two bases with the included sync cable and now both halves will move together in unison. Both remotes will control the now synchronized adjustable base. If you’re using 2 Twin XL Mattresses: Join the two bases together with the included clamp and you’re done. By NOT joining the two bases with the included sync cable you may now operate each half independently with each remote.