SPROCKET 40MM HUB TRULLI/OTK BLUE https://www.agskartparts.com.au/products/2667/sprocket-40mm-hub-trulli-otk-blue
40mm SPROCKET HUB REVERSE HUB INSIDE SPROCKET OUT OR HUB INSIDE AND SPROCKET IN [ picture slightly different no OTK logo and that outer surface machined to alloy]