Ride the entire mountain without breaking the bank. The STR is the perfect introduction to Union's all-mountain binding category. Ride the entire mountain without breaking the bank. The STR is the perfect introduction to Union's All-Mountain binding category. A responsive Stage 5 Duraflex baseplate, paired with the supportive S11 Duraflex highback, and super durable Exoframe 2.0 ankle strap, will keep you feeling locked in and ready to power through whatever the mountain can throw at you.