West System G/Flex 650G flex 650 has the ability to make structural bonds that can absorb the stresses of expansion, contraction, shock, and vibration. This epoxy is resilient and impact resistant. With a modulus of elasticity of 150,000 psi (WEST SYSTEM 105 Resin 205 Hardener has a modulus of elasticity of 450,000 psi), G flex is more flexible and can deflect further before breaking than WEST SYSTEM 105 205, while being much stiffer than typical adhesive sealants. G flex