The mainstay tool of the Fixed Gear rider, the 15mm Spanner is an indispensable item to have with you. The 15mm spanner is simple; it doesn’t need a bottle opener on it or a fold out chain tool, it just needs to work really well. So they added a dual-directional 15mm Socket Wrench (ratchet spanner) to the other end, so as you don’t round your nuts off. It's also long enough to give you plenty of leverage and small enough to tuck away in a pocket. What more could you want?