Type I
Also known as an offshore lifejacket, Type I personal flotation devices provide maximum buoyancy and are recommended for rough, open or offshore cruising when rescue response may be slow. Designed to turn most unconscious wearers from a face-down to a face-up breathing position in the water, Type I PFDs are bulky and somewhat uncomfortable for watersports.

Type II
Also known as a near-shore lifejacket, Type II personal flotation devices are intended for calm, inland waterways and circumstances when prompt rescue are likely. Designed to be worn around the neck and strapped around the torso, Type II PFDs will turn some (but not all) unconscious wearers from a face-down to a face-up breathing position in the water.

Type III
Also known as a flotation aid, Type III personal flotation devices are intended for calm, inland waterways and circumstances when prompt rescue are likely. Type III PFDs are designed to offer maximum comfort and freedom of movement (i.e. watersport jackets and vests), but require users to place themselves in a face-up breathing position in the water.

Type IV
Also known as a throwable device, Type IV personal flotation devices are intended for calm, inland waterways with plenty of boat traffic and where help is always available. Type IV PFDs are designed to be thrown to a person in the water and grasped and held by the user until rescued. It is not designed to be worn. Type IV devices include buoyant cushions, ring buoys, and horseshoe buoys. For paddling and rowing, Type IV throwable devices are best used in conjunction with a wearable PFD since they are not USCG approved for canoe and kayak use.

Type V
Also known as a special use device, Type V personal flotation devices are highly specialized vests designed for specific watersport activities such as waterskiing, board sailing, and paddling. Type V PFDs provide the performance of either a Type I, II, or III PFD (as marked on its label) may be worn instead of another PFD only if used according to the approval condition(s) on the label; otherwise they are not considered USCG approved.

Size
When selecting a PFD, size is very important. It must fit properly to work properly, so you must make sure PFDs are the right size for the individuals who will wear them.

U.S. Coast Guard weight guidelines:

• Infant (0-30 pounds)
• Child (30-50 pounds)
• Youth (50-90 pounds)
• Adult (over 90 pounds)

While determining correct fit, it is also important to consider comfort. A personal flotation device should be sufficiently snug to prevent the user from slipping down, but if it is too tight it will be uncomfortable and will likely be removed. Follow the adult sizing guidelines for each product to find the PFD best suited to your body type.

Children should always wear PFDs. In many states it is required by law. Bearing this in mind, it is important to size children's personal flotation devices correctly. Infant PFDs should be designed with flotation collars to keep heads out of the water and crotch straps to keep the PFD in place. Follow the weight guidelines for each product to help you determine which size to buy.