SUR-FIT Natura Two-Piece Durahesive Skin Barrier. The SUR-FIT Natura Two-Piece Ostomy System is ConvaTec?s most extensive two-piece product line. The SUR-FIT Natura Flange System signals a secure, accurate closure with a series of audible clicks". A simple snap-off, snap on design allows users to change the pouch quickly to match activities without removing the skin barrier from the skin. Durahesive skin barriers are designed for people whose stoma output is mostly liquid. Unlike other skin barriers that can break down around liquid output, Durahesive skin barriers swell up to protect the stoma. This special effect, called turtlenecking, helps create a more secure seal without harming the skin. Durahesive skin barriers are also easy to fit, apply, and remove. They will adhere securely to the skin while showering, bathing, and swimming.