The Double Hander Threader is a 34% smaller version of the Triple Hander Threader. The truth is, this version is a substantial hold. It's big in that you can easily hold on to it on a roof. You can toe hook it, and you can bicycle it.
The tapered design allows you to adjust its difficulty on different wall angles though it is best suited for roofs.
Your hand will slide down to the lowest point in a roof where the diameter of the hold is 2" inches. A child will easily grab it.
The taper of where you grab runs from 1-3/4" inches to 3" inches in a vertical orientation. If you flip it upside down, you can get your hand down to the 1-3/4" portion of the hold.