This cylinder is compatible with MIT 70 PFD model numbers MD4041 and MD4042. Use only Mustang Survival rearm kits. Use of other rearm kits may result in improper operation or failure to operate and will void the product&';s warranty. Regular maintenance can reduce the possibility of inadvertent inflation. For a maintenance schedule, refer to your owner&';s manual. You should rearm the inflator before the expiry date on the cap passes. Features This rearm kit contains: One 17-gram CO2 cylinder One automatic inflator bobbin (use only with MIT 70 MD4042 automatic only) Rearming instruction manual