Rockwool Unfaced CurtainRock 40 - All Sizes Thickness:4 in The side rails are integrated

The side rails are integrated into the bottom sash and extend during its opening

While some customers have noted that the product can be slightly itchy when handling

It has built-in flashing

Rockwool Comfortbatt R23 insulation is suitable for use in exterior walls

Rockwool Unfaced CurtainRock 40 - All Sizes Thickness:4 in The side rails are integratedRockwool CurtainRock is a lightweight, semi rigid stone wool insulation board designed to meet a variety of curtain wall specifications. Rockwool Safe is UL and Intertie approved as a forming material for numerous fire stop systems. Rockwool Safe together with CurtainRock 80 provides a comprehensive critical line of defense in fire protection that has been UL ULC tested and approved for perimeter fire containment. Thickness Sq Ft Pack 3" 40 4" 40 5"