Dynatrol I-XL FTH is field tintable and based on a unique hybrid STPU (silyl-terminated polyurethane) differentiating it from the standard Dynatrol® I-XL urethane-based sealant. The STPU chemistry utilized by the Dynatrol I-XL FTH formula allows for a low odor, non-staining, non-yellowing, one-part, moisture curing, gun grade, isocyanate free sealant. It has been developed specifically for sealing dynamic joints between dissimilar materials, of varying coefficients of expansion and contraction on both porous and non-porous surfaces. It cures to a low modulus rubber with extraordinary adhesion, capable of accommodating joint movement of ±50% of the original joint width. It does not yellow, crack or craze on long-term exposure to UV light.