GoPro Handlebar Seatpost Pole Mount GRH30 Seatport Attach your GoPro camera to handlebars, seatposts, ski poles and more. Fits 0.75 to 1.4 1.9cm 3.5cm diameter tubes. You can also clamp to chainstays, small roll bars, bolt-heads, windsurfing and kitesurfing control bars, or even use to create a handheld boom any pole that is in the size range above. Revisions to the existing Handlebar M