All trees purchased come with the hubs necessary to create our full 360 degree trees. However, if you want to save space and put your tree against a wall the "Wall hubs" are perfect. Just purchase one Top Wall hub for a single tree and use in conjunction with the correct number of Standard Wall hubs. 1 Standard wall hub is required for a small tree, 2 for a medium tree, 3 for a large tree and 4 for an extra-large tree.