This 39adda39 is an additional free standing storage unit for use with both nxt gen and tc topstore containers and accessories additional 39addas39 such as this are designed to be used in conjunction with topstore spacemaster starter kits to increase the amount of storage space the kit offers there is no limit to the amount of 39addas39 you can add so you can tailor your kit to suit your needs by buying the right amount of 39addas39 to suit your requirements