Flexi-Brick uses a thick skin of 2" thick extruded polystyrene. Polystyrene has twice the density of leading surround skins. Flexi-Brick comes with four Finger-Lock sides, steel supports, and a 26 ga. Steel chimney crown that has been coated with mortar to give a concrete appearance. This surround won't peel, rust, or fade. Flexi-Brick is available in an unlimited amount of customer sizes, with a turn around time of 3-7 business days. Several additional colors are available factory direct. This item includes mortar to seal joints and hardware pack.