Birkenstock Shoes New Birkenstock Oswego Narrow Slip On In Birkenstock Shoes Birkenstock Oswego Leather Slipon Shoe Poshmark Birkenstock Shoes Birkenstock Oswego Slip On Size 4 Poshmark Oswego Suede Leather Light Rose BIRKENSTOCK. The casual low shoe features elastic inserts which make it easy to put it on and take it off in no time. The flexible rubber sole with a shock absorbing cork PU intermediate layer and the padding at the edge of the shaft result in even more comfort. The upper is made of high quality, soft canvas.