I wanted a platform onto which I could strap my waterproof phone case. Existing bike phone clamps are good, but they leave the phone open and exposed to the elements. I wanted to re-use my Karrimor iphone arm case on the bike. Phone stays in it's usual case, pop it into the waterproof case, strap to platform. Platform cable tied to bike - use strip of rubber to prevent slip, and cable ties. Designed for tube diameter 35mm aprprox. Sketch file included.