Convatec Sur-Fit Natura® Two-Piece Durahesive® Skin Barrier. 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.