Birkenstock Boston Essentials EVA Clogs. Our best-selling clog in an ultra-lightweight style. The Boston EVA is made from water-friendly material, giving you a flexible design built on the contoured footbed you love most. The perfect pair for pre-workout, post-practice and all the rest days in between. Contoured footbed for legendary Birkenstock support. Style made from single piece of EVA. Water-friendly, flexible & lightweight. Adjustable strap with tonal pin buckle. Imported.