The Mortise Eyegear "system" consist of a frame, 3 pair of polycarbonate lens, and carrying pouches. The lens are user changeable just by popping them out and replacing them with ones appropriate for the lighting condition.
The lens are locked in place by two notches: the hook at the hinge end and the half circle at the nose pad end. The hook goes in first. In the left photo below, you can see the "catch" inside the frame on the nose pad side. The lens should slide and click into that to secure itself to the frame.
The nose pad material is soft. According to the 180s website, the hydrophilic material is suppose to provide MORE adhesion as you get sweatier! What a great idea... we'll let you know how well they work in practice after our runners have had a chance to check them out.
The Mortise came with the temple folded in front of the lens. This is 180s' patented "Pivot Guard System". The idea is to use the temple pieces to protect the lens during storage. By allowing the arm to fold in front, the whole package also has a more streamlined profile.
With the pivoting hinge approach, 180s addressed three different design issue at once: storage size, temple breakage, and lens protection. Nice!
In the end, the most important criteria for a great pair of sunglasses is fit. If they are not comfortable, it is difficult to wear them on the move.
The Mortise was outstanding in the area of fit. These glasses weighed in at less than an ounce. The flexible temple easily kept them on our heads... no matter their size!
As to their comfort while just sitting around during a July 4th cookout...they were outstanding! We'll take them out for a run to check out 180s' performance claims. We should have the First Use review done by the end of July.