Pro build trays now come in a variety of capacity settings. The new firmware for the Pro1 and Pro2 machines has greatly enhanced the life of these trays. You can now choose to have a money saving, higher capacity for each tray. The trays are all made of the same material but some people get more life out of their trays by optimizing settings of the glass slider on their machines. The new software and firmware allow these improvements. We now sell these trays a single units rather than sets as a result of the software and hardware improvements. We also have 1L, 2L, and 5L trays available as well.