With over 60 years of diving experience and having sold almost every full-face mask (FFM) on the market, it was easy to see there was a need for something better. A common problem with most FFM is the seal. The lack of a good seal causes the diver to use air quicker and can interfere with the diver's ability to hear if using underwater communications. With that in mind, the GFFM was designed around a double seal. This along with many other great features (i.e. semi positive pressure, quick release 2'nd stage, easy maintenance, etc.) is why you will find the Guardian is the best choice for your money when looking for a full-face mask. The double seal 55-60 shore liquid silicone skirt with high strength polycarbonate visor (lens) was specifically designed to allow people with a small face or a slim face, especially in the temple area, to seal better. Everyone has a little different face. As divers you all know how important being able to equalize is. Equalizing is a challenge for all full-face masks. One size does not fit all! in to ensure everyone can equalize, OTS has put together an equalizing kit which comes with every Guardian full-face mask. The kit consists of two bases. One is a standard size without any holes. It can be adjusted up or down to fit as necessary. The other base has two holes which allow for different size pads that can be added. In the event the standard base does not work for you, one of the pads and the other base should fit the bill.