From the manufacturer:
"Birkenstock Mayari"
"Like A Thong Only Different. The Soft Toe Loop Sits Gently Across Your Toe And Won'T Rub Or Pull. Two Fully Adjustable Allow For Precise Adjustment And A Secure Fit. Classic Birkenstock Footbed, Pronounced Arch Support, Deep Heel Cup, Raised Toe Bar And Neutral Heel. Fully Repairable, Made In Germany."