What is the thickness of the back of the support between the wall of the cupboard and the edge of the glass shelf please? These are to be used to replace similar supports in a bathroom cabinet. The internal width of the cabinet is 278 mm. The existing glass shelves are 270 mm wide. The original supports were 1.5mm thick, (but that's where they've broken!) I need to be sure that the glass shelves will fit back into the cupboard without having to cut a bit off the glass. Thank you.