Convatec SUR-FIT® Natura® Two-Piece Cut-to-Fit Durahesive® Skin Barrier 2-1/4" Flange Size, 4" x 4" Red The SUR-FIT® Natura® Ostomy System is a comprehensive product line with our latest skin barrier technologies. The plastic coupling ring allows the pouch and skin barrier to snap together for audible security. Durahesive® skin barriers are designed for people whose stoma output is mostly liquid. Unlike other skin barriers that can breakdown around liquid output, Durahesive® skin barriers swell up or "Turtleneck" to further protect the stoma and peristomal skin.