Keyboard Clamp Rail Set, Heavy Duty Metal Keyboard Slides Mounting, Under Desk Pull Out Slider Track with C-clamp Mount System, for DIY Under Desk Kitchen Cabinet Drawer Keyboard Tray(Size:12 inch)

Just the job, great add on and does exactly what it says.

The measurements aren't particularly clear in this listing:From the top of where it clamps the desk to the point it screws into a board is 6.5 inches / 16.5cm, so that should help you factor any leg room that you lose from a desk / standing desk.When fully extended, the board you fit (doesn't come with it, obviously) will extend by 8" / 20 cm.Literally no part of this is 12 inches when opened or closed. When assembled and open the full mechanism is just over 16".I was hoping for a sturdy drawer mechanism that extended by 12 inches to fit a midi keyboard on (as it does have a significant height drop that allows for keyboard clearance), but unfortunately it's not fit for that purpose. I had a quick go at typing on it but found it to be somewhat wobbly and unusable.

Great product, works a treat. If I had a little grumble, it could do with a basic set of instructions, so no need to look back at Amazon pictures to give you a clue.

It's just the rails and mine arrived with no instructions which made it into a bit of a puzzle to assemble. Once I bought a seperate shelf and eventually worked it out, it works great. If I was to choose again I'd pay a bit more and get one that came with a shelf as it didn't save me much buying separately.

Rails are different from ones pictured so was a faff trying to figure out how to put together,also was missing the scews.would not buy again.clamp is solid enough