ERS4 Swim Fins by ALLY uses a proven fin design that's been refined with high performance rubber that offers optimum thrust, power, and comfort.
ERS4 feature: 
Comfortable foot pocket and "v" ankle strap 
Functional toe-exit drain hole
Traction Foot Pocket
Explosive Power
Made of Natural rubber that floats well in the ocean.
SIZING:
SMALL // MENS 5-6.5 // WOMENS 6.5-8
MEDIUM // MENS 7-8.5 // WOMENS 8.5-10
MEDIUM-LARGE // MENS 9-10.5 // WOMENS 10.5-12
LARGE (11-12.5)
X-LARGE (13-14)