http://www.ebay.co.uk/itm/Fg-Steel-Spur-Gear-48t-19t-Pinion-Gear-Not-Plastic-Spur-Gear-Fg-Alloy-/330885292141?_trksid=p5197.m1992&_trkparms=aid%3D111000%26algo%3DREC.CURRENT%26ao%3D1%26asc%3D14%26meid%3D6103637740434610404%26pid%3D100015%26prg%3D1006%26rk%3D1%26sd%3D330885292141%26
One of these and do I need 48 / 18 ?