This super versatile, super strong T clamp lets you attach two 7/8 inch (22.2mm) tubes or two 1 inch (25.4mm) tubes at 90 degrees to each other. 

One end of the T-clamp goes inside of and clamps to one of the tubes, while the outside of other tube is clamped by a discreet but sturdy machined arch. You are free to choose which tube gets clamped which way. The 7/8 inch and 1 inch size means it's useful in all kinds of places. We use this clamp on our neckrest mounts, SeatSide mounts, and we even use it to make display stands when we go to shows. Note: that this clamp is designed to hold accessories; it is NOT designed to hold handlebars in place.