they are cncd plastic mounts for the front of the gearbox and rear of the motor. The plastic is fairly soft, so doesnt break.
They work really well at absorbing the shocks to the drive.
The steel ones on that website will bend and jam up your wheels, if you weld cross braces to stop this, they will be too stiff and youll break the drills.
Up to you, but I strongly recommend either plastic mounts, or soft bouncy wheels, to keep your drills in one piece when you get flipped or hit.