Single Foam & Silicone Seal FlexiFit™ 406. The FlexiFit™ 406 Petite Nasal Mask offers an over-the-nose mask solution specifically designed to fit finer featured faces. The Petite design is small, light and easy to use. The Stretchgear™ Headgear provides even greater comfort and the maintenance-free bias diffuser ensures a quieter operation. The FlexiFit™ 406 Petite Nasal Mask comes as an Out-of-Box Solution fully assembled and ready for use.