You want them water tight but not choking-tight. Trim them by using good scissors or a razor blade to cut away concentric circles of gasket until you get a fit you like. Some have ribs to give you a guide.
AHA! so thats how that works. i tried to wear it for awhile and my face was turning purple! my wife suggested i take the suit off before i pass out. it was one of those lmao kind of moments!! thanks for the advice.
