BAL FastFlex is the one to use when your substrate might bend or expand; this is a cement-based adhesive with added polymers, which give it super-flexibility. This makes it useful for projects where your substrate may shrink or deform over time and where you are worried about a conventional adhesive cracking or coming loose.BAL’s technical data says that this adhesive can deform by ±5mm. BAL FastFlex is suitable for indoor and outdoor use.  Mix carefully with water to make a smooth paste. Offers an open time of 20 minutes (ie the time, after application, when the adhesive will make a good bond with tiles placed on it).  FastFlex does set quickly - this is one of its virtues, but it does mean that it lasts less long in your pot and you may need to make up a new mix more often than with other adhesives. Can be used with ceramic, porcelain, vitreous glass and some natural stone tiles. Ready for grouting in 5 hours. Coverage approximately 0.5m². Supplied in an oblong resealable plastic ice cream-style tub. Weight 800g.