The navy, medium adult "Hit Air" vest fits me perfectly. I am 5.8", wear a 8 or 10 blouse or size Large t-shirt. This buckles perfectly around my torso and feels "fit" not loose or tight. I also purchase two additional cannisters. I hope I never experience what this vest can do, but I am a more confident with wearing it. I use it every time I mount my horse. The wait was worth it.