New Hejnar Photo 90 degree mounting block with anti twist island for connecting various rail at 90 degree.This is similar block to my 101A item. Ii is 1.375 wide compare to 1.00 on G101A. All the corners and edges are rounded for the safety to prevent from accidental injuries or damages to the other equipment. Island on black is 0.212 inch wide and snap perfectly in any current products/rails from Hejnar Photo. Other rails from different manufactures may have slot smaller and black will not connect correctly so please check your rail if you are planning to use it with product other than Hejnar Photo. In such situation you can use 90 degree block without anti twist future (part G101) All the corners and edges are rounded for the safety to prevent from accidental injuries or damages to the other equipment. This small block can help you build base for panorama system , L bracket for camera , it can be used with Long Lens Support Bracket ( LLSB) if your rail does not have hole where LLSB can be mounted or you rather use 3/8 rails without taped hole on end.