Mustang Survival Re-Arm Kit "B" 33 Gram Auto-Hydrostatic. This rearm kit is compatible with inflatable PFD model numbers MD5283, MD5253, MD6284 and MD6254. 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. The Auto Hydrostatic inflator cap and body should be replaced before the expiry date on the cap passes.