This is an optional Tekno RC ET410 Rear 3.5mm Pin Suspension Arm Set, intended for use with the ET410 Competition 1/10 Electric 4WD truggy to improve the durability of your kit. The arms have been modified to accept the larger HD 3.5mm hinge pins that were introduced with the EB410.2. Not only have the arms been updated to fit the HD pins, additional material has also been added around the hinge pin area for added durability.