G Funk bar clamps
The G Funk is a two part clamp design that's designed to allow you to fit a Strapdeck in front of or below your bars in order to strap something like a drybag to it for solid-no-wobble-or-shake carrying goodness. Clamps are 31.8mm to fit either side of your stem on almost all modern bars.
**NOTE THIS IS FOR THE 2 X CLAMPS ONLY, STRAPDECK AND STRAPS ARE AVAILABLE SEPARATELY**
There's a little bit of extra info on drJ0n's blog that you may find useful here :
31g for the pair including mounting hardware
The best StrapDeck for this is the Large, the recommended straps (alu or nylon) would be 20" if going round your pack and the Strapdeck, 25" if going round the bars too.