Abstract: A seal and a respiraoty mask having a seal adapted for confronting engagement with a surface of a user to form an interface therewith. The seal includes a first portion defined by a gel substance. In one embodiment, the seal includes a selectively formable substance adapted to be molded from a first pattern into a second pattern and to retain the second pattern responsive to being so molded. The seal and mask having the seal in this embodiment is tailored to patient by causing the formable portion of the seal to be placed in a malleable state, applying the seal to the patient while the formable portion is in the malleable state, and causing the formable portion to be placed in a fixed state to retain a shape generally conforming to the portion of the patient underlying the seal.