From the top of an unwrapped 24mm diameter handlebar (the diameter outside of the tapered region) to the underside of the extension clamp is about 30mm. It's about 35mm to the underside of the armrest pad. Keep in mind that bar tape will affect that measurement. 

If you're going to fit your hands under the pads, we suggest installing spacers - you can purchase these directly on our website here: https://redshiftsports.com/extension-riser-kit-for-qr-aerobars