We highly recommended using Kelly's Cork Renew for your Birkenstock sandals! Kelly's Cork Renew prolongs the life of your shoes with cork footbeds by keeping out the moisture. Cork Renew protects, preserves, waterproofs and seals cork footbeds. This non-solvent, water-based formula will help keep the cork from crumbling, drying out or breaking down. The Cork Renew dries clear and comes with an applicator brush for easy use. Packaged in 2.4 ounce bottle.