This Custom Building Products FlexBond 50 lbs. Fortified Thin-Set Mortar is a premium-quality, polymer-modified mortar with exceptional flexibility and bond strength. FlexBond is perfect for tiling difficult surfaces, such as plywood, vinyl and laminates and for hard to bond non-porous tile such as porcelain and glass. FlexBond protects against cracking caused by minor in-plane surface movement.