Matsuda M3147 Sunglasses Lens:Café Blue Gradient while the 51mm suits medium

while the 51mm suits medium and smaller faces

Look at the hinge

and 145 is the length of each temple arm

Sizing: 56-15-145 means a 56mm lens width

Sizing is 51-21-145

Matsuda M3147 Sunglasses Lens:Café Blue Gradient while the 51mm suits mediumLens quality is the quiet argument for the M3147: it ships with premium anti reflective coated lenses, which cut the back glare that bounces off the inner surface of a sunglass lens and sits in your peripheral vision all day. The frame around them is engraved titanium with precious metal finishing, built in Japan. Sizing: The 55 17 145 numbers are lens width, bridge width and temple length in millimetres. A 55mm lens is a large eye size, and the 17mm