ProSeal XL4 is available in cans, AND Direct Inject! ProSeal XL4 Cans: Not to be used with ammonia. This product is for large A/C systems (up to 5 tons) ProSeal XL4 is designed for repairing leaks in condensors, evaporators, copper line, and solder joints. This product is an epoxy that reacts to water and air. When coming in contact with the atmosphere, it forms a seal over the leak. If your system stays charged for one day when running, this product will fix most leaks that you encounter. If there is air and water in your system, pull a deep vacuum on the system and boil moisture out of the system. An alternative to pulling a vacuum is to purchase and use ProDry XL4 to turn moisture into synthetic oil. This will prevent ProSeal from reacting inside your system. If using the airosol can in a R410 system you must take the low pressure to UNDER 50 psi. When using Direct Inject you do not remove any refrigerant from your system. In most cases. if a system has not leaked below 15 psi, there is typically not air or moisture in the system. The system has greater pressure than what the atmospheric pressure is and cannot leak unless the system is below 15 psi. ProSeal XL4 has twice as much sealing agent as regular ProSeal. It is great for repairing those reoccuring leaks in systems. Save on costly repair and use ProSeal XL4 instead. Made for large systems (5 ton a/c's)