Custom. It started life as a tronxy x5sa-400 but I think only 2 steppers and the frame are original still. I changed the bed to a 16"^2^ *3/8 thick aluminum tool plate about 5 years ago. It always worked well for me. Unfortunately the silicone mat I used doesn’t seem to be made any more. I’m going to try one meant for a creality cr10 S4. I may have to re-machine the mounting holes for the thru holes on the mat tho.