Spy is a brand of sunglasses. Like all other models of sunglasses, they are replaceable. Also, as long as you have a set of frames that can fit the Spy brand, you can replace your current lenses with Spy lenses. Replacement Spy lenses are available for the Diablo, Mach 2, and HSX models. They can be ordered through the Spy company directly online by contacting their customer service line. After receiving the replacement lenses, changing your current glasses to Spy lens glasses is a fairly simple process.
Remove the old lenses. Hold a lens with your finger and thumb. Apply pressure either forward or back until the lens releases with a popping sound. Do the same for the other corners. Apply pressure in the same direction in which you applied it to the first corner. Repeat this for the remaining lens.
Determine which Spy lens goes on which side of the glasses. The right lens will have to be on the right side and the left on the left side. There is no option to reverse sides. Hold the lens up to the front of the frames with the outward curve of the lens facing forward. You will be able to determine the sides by comparing the shape of the lens to the shape of the frame.
Press the lens into the correct side of the glasses. Hold a corner of the lens with a thumb and finger. Press the corner into the coinciding corner of the frame. The lens will pop into place. Repeat this for all corners. Do the same for the remaining lens. The process is the reverse of what was done to remove the lenses.