I think it's all 1 1/2" stuff that they used (I'm using the same for my neoprene boot / glove dryer :wink: ). I used small-diameter irrigation-grade pipe (1"?) for my cart, which is perhaps a little less beefy but folds up very small to fit inside my 9.5" round hatches, and it takes up very little room when stowed in the kayak. I've reinforced the cart with 1/2" aluminum rod inside, which makes for a strong axle and support stays. The support arms (which the kayak rests on) are the same 1 1/2" PVC as Dan's cart. I've had my loaded Romany on it quite a few times - weight must be easily over 100 lbs - and while I have to be a bit careful due to the solid (non-pneumatic) wheels, it's fared very well so far. It took a few design improvements, but the current one has been in active duty for well over a year with no problems at all.