Answer:
Passenger's body weight and chest size
Step-by-step explanation:
Finding a PFD (Personal Flotation Device) for a passenger requires you to find a PFD which fits the person properly for his/her required weight. There are three categories of sizes:
Men's size varies from small to 3x large where the chest size varies and the weight of the person is over 90 lbs or 41 kg
Ladies size varies from x small to x large where the chest size varies and the weight of the person is over 90 lbs or 41 kg
Kids weight varies from 90 lbs or 41 kg to 30 lbs or 14 kg
The PFD need to snugly fit to the person's body. So, to get the best fit you need to find the weight of the person and the corresponding chest size.