These are the standard river guide sandal. They are better than Teva sandals for durability and comfort. The Z1 has the advantage over the Z2 of more easily allowing a neoprene bootie to be worn in the sandal but the Z2 which has the toe loop is more stout for hiking. No matter what, the straps will eventually break near the big toe area. Chaco will repair them at a cost. Also, to fight this, Chaco recommends 'flossing' the sandal strap in soapy water to remove sand which breaks the strap down. I have had 8 pairs of these things in 15 years and continue to buy them because there really is no better sandal for river guiding.