The Wheelchair Tube Clamp is casted from lightweight aluminum and can be tightly mounted onto wheelchair frame tubes to provide a very stable base. Given that there is no universal diameter for wheelchair tubes, three plastic spacers and a rubber strip are included allowing the clamp to fit 3/4" (19 mm), 7/8" (22.2 mm), 1" (25.4 mm), 1-1/8" (28.6 mm), 1-1/4" (32 mm) tubes. The clamp is equipped with a ball head that can be directly socketed into compatible arm attachments such as the Super Knuckle Arm.