Hi Gully - Will probably buy 20mm from BST Automation. I have 10mm belt/pulleys all set up on motors and mounts from a prior build. Will use these. I have been surprised on how well they performed routing (the motors have 10:1 gearboxes on them and they are mighty strong). The little machine was intended for laser/knife/plotting but everyone wanted it to be a router so I mounted a router on it. So maybe a half sheet is better for 10mm belts. My other machine had 16mm and if building from scratch I'd probably go 25mm if using belts again especially now I have now found an Asian supplier of belts/pulleys vs Oz suppliers. .. I think my second grade gantry is 1450mm capable... It maybe a long, thin machine as I want a machine for making gantries and hydrofoils but the aim is to use up all surplus parts and on-sell, then maybe make a mill. But the main rule for Frankenrouter is to make the parts myself so have to finish YaG first. Peter