How does it work and can you use it over and over?
When the inflation kit that is supplied with the vest is activated, either in use or through testing, it must be replaced with a new kit. The old CO2 cartridge and pin are removed and this replacement is inserted in the vest pocket. It can be used only one time. Once the CO2 cartridge is punctured to inflate the vest, it must be replaced.
Will this fit a Halkey Roberts 9000 and if not what is the part number for the correct rearming kit?
The Halkey-Roberts V90000 inflators are available for 3/8 and 1/2 inch threaded cylinders. You will need to know the model of your life jacket to know which cylinder capacity and thread size you need.
Will this kit fit a sterns throwable life ring 16 gram model# I901kit -00-000?
All of the PFD rearming kits are chosen based on the following; is the neck threaded or bayonet type? What is the gram rating (16g is good here) and the diameter of the neck (this one is 3/8") If your life ring has a 3/8" threaded neck, this one should fit. A search of the Stearns website did not locate the product you are describing.