Because they are kevlar-reinforced, it is very rare for the belts on MakerGear 3D printers to be damaged. If your belts are worn, check your printer for alignment issues—misalignment is the most likely cause for worn belts, and should be addressed in order to maximize the lifetime of your belts.
The M2 belt set includes both belts used on the M2 and M3-SE rev 0 3D printers ( 630 mm for the X-axis and 702 mm for the Y-axis).
The M3-SE belt set includes both belts used on the M3-SE rev 1 3D printer (742 mm for the X-axis and 702 mm for the Y-axis) .
The M3-ID belt set includes all three belts used on the M3-ID 3D printer (742 mm for the left extruder, 726 mm for the right extruder, and 702 mm for the Y-axis).
The Ultra One belt set includes all four belts used on the Ultra One 3D printer (2 Y-belts, 1 X T0 belt and 1 X T1 belt).