Women's Rainbow® Leather Double Layer Arch Flip-Flops. The Rainbow® Willow is more than a sandal, it's a custom footwear experience. Featuring the new Rainbow® Double Layer Arch, the extra layer starts at arch and rises to heel to provide those with higher arches more support. The new midsole design should break down 10% under your foot to provide and exact mold for a custom feeling fit. Get more than you expect from flip-flops by buying the Rainbow® Willow today!