[sebbie]

Liners are made from smoother all nylon than the Lycra blend used for the suit itself. This in part is a comfort issue, especially for guys who typically put their penises in an "up" position, with the ultra-sensitive underside pressing tight against the nylon of the liner. The liner also plays a role not only in reducing transparency when wet. but also reducing the visibility of the outline of the shape of the guy's penis even when the suit is dry. Some guys think its fun to be visible, and cut out the linings. But some suits are sold that do not have any lining.