Flex reffers to the stiffness of your fins and you will find that as your bodyboarding improves you are likely to want stiffer fflex. V3 Models have the same foot pocket as the V1 & V2 but has a stiffer rubber on the bottom foot pocket to improve the power en maintain the commfort thanks to the neoprene piece inside. 
VULCAN V3
V3 MOULD
3 rubber hardnesses for optimum performances
Inside neopren pad
Ergonomic Foot Pocket
Optimum Drainage system
Anatomically designed strap
Made with premium quality Malaysian Rubber
 
Size :
S (US 6-7 | EUR 39-40)
M (US 7.5-9 | EUR 40.5-42.5)
ML (US 9.5-10 | EUR 43-44)
L (US 10-11.5 | EUR 44-45)