If you ride an Aztek Siren 1 or Siren 2 deck and want to convert your conventional 8mm axle to 12 STD, you need to pick up Aztek's 12 STD conversion kit. DOES NOT WORK WITH THE SIREN 3 DECK. Before you convert your deck to 12 STD, make sure you plan on picking up 12 STD forks, too. Otherwise you'll be running 12 STD out back and conventional 8mm up front. The kit includes new dropout inserts, a 12mm axle, and axle spacers.