What is Build size in mm?

Build size in mm is the longest side of the working volume, so it sets the largest object a printer or engraver can handle at a time. Bigger is not automatically better: a larger bed needs more desk space, more levelling and a firmer surface. Anycubic leads here with 500 mm, ahead of ACMER at 400 mm and Bambu Lab at 350 mm. ALTERNATE's Creality listing gives 300 mm and Artillery3D 260 mm. Size your choice to the largest job you actually plan rather than the biggest figure on the sheet.