The GSI AH50 hub extension is the perfect add on to your GSI wheel. It extends the shaft by 50mm. Three 5mm non-threaded holes and three M5 threaded holes for 70 and 50.8 Pitch Circle Diameter on both sides gives you the most flexibility and strength. Constructed out of billet 6061 aluminum with models anodized in Purple, Gun Metal, Black, Red, Blue, Gold and Green.