I have the 40mmx40mm BOAB bars pictured. Very heavy duty, very simple. It's not hard to get the bars level, it's just something to be aware of. The width also changes slightly but that's less likely to catch you out. My front most bar that I have my antenna mounted on is so far forward it would be tipped forwards by the angle of the gutters so I just used an angle grinder to adjust the angle of the feet to level it out.