Inflatable Life Jacket Rearming Kits

By Brian Gordon, Last updated: 5/21/2026

Why Rearming Your Inflatable Life Jacket Correctly Matters

An inflatable PFD that has not been properly rearmed with the correct kit will not inflate reliably in an emergency. The CO2 cylinder, bobbin, and inflator mechanism must be matched precisely — an incorrect cylinder neck diameter will not seat, a mismatched cylinder weight will underinflate the bladder, and the wrong bobbin type will not activate the correct inflator mechanism. This is not interchangeable gear: using the wrong rearming kit on an automatic inflatable life jacket is the same as having no life jacket at all.

Rearming is required after every deployment, after any accidental inflation, and as part of annual maintenance. The U.S. Coast Guard requires inflatable lifejackets to be serviced annually and maintained in accordance with the manufacturer's instructions (46 CFR Part 160, Subpart 160.176). Failing to rearm or service an inflatable PFD means it cannot legally count toward your vessel's required carriage of USCG-approved life jackets.

How to Identify the Correct Rearming Kit

The correct rearming kit for your vest is determined by three things: the inflator type and model number, the cylinder neck diameter, and the cylinder weight (in grams). All three must match exactly. The inflator type and number are printed on the inflator mechanism itself. The cylinder weight and neck diameter required are printed on the bladder or inside the cover of your inflatable life jacket — check there before ordering.

Identify your inflator from the images and style numbers above. The cylinder weight and cylinder neck diameter that will fit your inflator are printed on the bladder or inside of your inflatable life jacket. Rearming Kits contain the items required to rearm your vest, including cylinder, bobbins, pills and green pin as necessary. Complete instructions on how to rearm your inflatable vest are also included.

Understanding the Components in a Rearming Kit

Depending on your inflator type, a rearming kit will contain some or all of the following:

CO2 cylinder — the gas cartridge that inflates the bladder. Cylinders are single-use only. Once discharged — whether in an actual emergency, an accidental inflation, or a water test — the cylinder must be replaced. Never reinstall a pierced cylinder. Cylinder weight (24g, 33g, 38g) determines how much gas is delivered; using an undersized cylinder will result in incomplete inflation. Manufacturers including Mustang recommend replacing CO2 cylinders every five years even if unused, as corrosion can compromise the seal.

Bobbin (water-soluble pill) — the automatic activation element used in bobbin-type inflators. The bobbin is a small cylinder of water-soluble material. When submerged, the white pill dissolves, releasing a spring-loaded pin that pierces the CO2 cylinder and inflates the bladder. Bobbins have an expiration date printed on them — if the date has passed, or if the manufacture date is more than two to three years old and no expiration date is printed, replace the bobbin regardless of apparent condition. As bobbins age, they can become sensitive to rain, spray, and humidity, increasing the risk of accidental inflation, or conversely may fail to dissolve quickly enough in an actual emergency. West Marine's own inflatable PFD inspection guide recommends replacing bobbins older than three years.

Green indicator pin or clip — a visible status indicator that shows the inflator is correctly armed. When the pin is in place and green, the mechanism is ready. A red indicator or missing pin means the inflator has fired or is not correctly assembled. Always verify the green indicator is properly seated after rearming.

Hydrostatic inflator cap (Hammar type) — used in hydrostatic inflators rather than bobbin-type systems. Hydrostatic inflators activate on water pressure rather than water solubility, which makes them less susceptible to accidental inflation from spray or rain. Hammar recommends replacing the hydrostatic inflator cap every five years. These kits require the complete inflator cap, cylinder, and key as a matched set.

Service Intervals: When to Rearm or Inspect

Follow whichever of the following applies first:

After every inflation — whether in an emergency, accidental deployment, or intentional water test. The CO2 cylinder and bobbin are both single-use and must be replaced before the vest can be considered armed.

Annually — inspect all components per USCG requirements and manufacturer guidance. Verify the service indicator is green, the CO2 cylinder is unsealed and uncorroded, the bobbin is within its expiration date and the white pill is fully intact, and the bladder holds air (orally inflate and let stand 16 hours — a sound bladder will hold pressure).

Every two to three years — replace the bobbin on bobbin-type automatic inflators even if it appears intact. BoatUS recommends a two-to-three year replacement interval; West Marine's inspection guide sets a three-year maximum regardless of apparent condition.

Every five years — replace the CO2 cylinder and hydrostatic inflator cap (Hammar type) per manufacturer recommendations, even if unused.

Automatic Inflatable Life Jacket Rearming Kits

Manual Inflatable Life Jacket Rearming Kits

Auto Hydrostatic Life Jacket Rearming Kits

*In the above three tables, column "PFD Brands Used With" is not all inclusive. Some rearming kits may be used with other brands and vests. Check your inflatable vest's product instructions for the correct rearming kit model.

Replacement Bobbin, Pin and Lever Kits

Frequently Asked Questions: Inflatable Life Jacket Rearming

How do I know which rearming kit fits my inflatable life jacket?

Three things must match: the inflator type and model number (printed on the inflator mechanism itself), the cylinder neck diameter (1/2" bayonet, 1/2" threaded, or 3/8" threaded), and the cylinder weight in grams. The required cylinder weight and neck diameter are printed on your vest's bladder or inside the cover. If you cannot locate this information, bring your vest to a West Marine store — our associates can identify the correct kit by examining the inflator mechanism directly.

How often does an inflatable life jacket need to be rearmed or serviced?

Rearm immediately after any inflation — emergency, accidental, or intentional test. Beyond that, the USCG requires inflatable lifejackets to be serviced annually. At minimum, inspect the service indicator (must be green), verify the CO2 cylinder is unsealed and uncorroded, check that the bobbin's white pill is intact and within its expiration date, and perform a bladder leak test by orally inflating the PFD and letting it stand for 16 hours. Replace the bobbin every two to three years regardless of apparent condition, and replace the CO2 cylinder every five years even if unused.

Can I use any CO2 cylinder to rearm my inflatable PFD?

No. CO2 cylinders that are not specifically approved for PFD inflation systems may not inflate the bladder correctly or reliably. The cylinder neck type (bayonet vs. threaded), neck diameter, and weight in grams must all match the specifications printed inside your vest. An undersized cylinder will not fully inflate the bladder. A cylinder with the wrong neck type will not seat in the inflator. Always use a cylinder from a rearming kit approved for your specific inflator model.

What is the difference between a bobbin-type and hydrostatic automatic inflator?

A bobbin-type automatic inflator activates when the water-soluble white pill (bobbin) dissolves on contact with water, releasing a spring-loaded pin that pierces the CO2 cylinder. Hydrostatic inflators activate on water pressure rather than water contact — they require submersion to a specific depth (typically around 4 inches) before triggering. Hydrostatic inflators are less susceptible to accidental activation from rain, spray, or humidity, and have a longer service interval: Hammar recommends replacing the hydrostatic inflator cap every five years, versus two to three years for bobbins. If your vest has a Hammar inflator (identified in the Auto Hydrostatic table above), use the Hammar-specific rearming kit — these are not interchangeable with bobbin-type kits.

What does the green indicator pin or clip do?

The green indicator pin or clip is a visible armed-status indicator. When correctly installed, it shows the inflator mechanism is properly assembled and ready. A missing, displaced, or red indicator means the inflator has been fired, was incorrectly assembled, or the CO2 cylinder has been discharged. Never consider a vest armed unless the green indicator is in place and visible. Check it before every trip.

Can I reuse the CO2 cylinder if my PFD inflated accidentally?

No. CO2 cylinders are single-use. Once the cylinder tip has been pierced — whether in an emergency, accidental inflation, or intentional test — the cylinder must be replaced along with the bobbin. Reinstalling a used cylinder in an inflator is not safe and will leave the vest unable to inflate in an emergency. Replace both the cylinder and the bobbin as a matched set using the correct rearming kit for your inflator.