The original that started it all. Known as the Birkenstock Fitness Sandal in Europe, this design tones the foot and calf muscles while improving circulation. This timeless one strap features our famous contoured footbed, fully adjustable strap and shock absorbing EVA sole. Available in a variety of materials and colors. Upper material: Birko-Flor - Made of acrylic and polyamide felt fibers, this material is a soft fabric with a smooth leather-like finish. Footbed: The original Birkenstock footbed - Featuring pronounced arch support, deep heel cup, and roomy toe box. Footbed molds and shapes to your foot. Sole material: EVA - Flexible, lightweight, durable and shock absorbing.