Snapxit are purpose-built emergency window safety devices specifically designed to break toughened glass. SnapXit H40A and H40H types are particularly Heavy Duty operators. Like all SnapXit’s, are permanently fitted and can be used on buildings, houses, boats, and buses. SnapXit's and HomeXit's are secured with a break-away seal and use a very strong 3M industrial adhesive tape which bonds the device directly to the window, permanently in place until it needs to be used. These amazing devices can be fitted in a few minutes to turn any appropriate window or glass wall into an emergency exit. So easy to install, no other equipment needed except for isopropyl alcohol, some lint free towel and a squeegee or scraper if you decide to fit the instructions sticker supplied. Operation is also easy: Break seal and strike the device with the side of your balled fist hard. More than one strike might be necessary depending on the glass. Very importantly, be sure they’re only to be used on proper thermally toughened glass. If the glass is properly thermally toughened, the H40A and H40H be effective on 28mm double pane insulated units (4mm / 20mm / 4mm) or up to 12mm thick single pane glass.