Anon M4 replacement lens comes in both Toric Spherical ( rounded ) or Cylindrical ( flat ) & both are compatible in the Anon M4 frame. Anon M4 lens feature Anon Magnatech technology, a industry first & the fastest interchangeable lens available on the market.  Anon M4 Lens has 8 magnets that strongly hold the lens on the frame and swapping lenses is very quick & easy.  The Anon M4 spare lens is injected & not stamped to eliminate optical distortion, these lenses combine de-centered  technology with a lens curvature that mimics the shape of the human eye for superior optics. The dual lens construction of the Anon M4 Lens ensures proper climate control between the lenses in all conditions, combined with Anons premium Anti-Fog coating that eliminates fogging. The Anon M4 lens is a strong polycarbonate lens that offers 100% UVA UVB UVC protection and exceeds ANSIZ87.1 impact standards.  Every Anon M4 spare lens comes with a really molded protective case.
ANON Zeiss Lens: Anon M4 replacement lens are premium lenses developed in collaboration with Carl Zeiss, world leader in precision optics. Carl Zeiss is synonymous with world class optics that deliver superior clarity & terrain definition, if you're looking for superior optics with enhanced contrast look no further then authentic Anon Sonar. 
M4 Toric Lens:  The Anon M4 Toric lens is a spherical rounded lens.
M4 Cylindrical Lens: The Anon M4 Cylindrical lens is a flat style lens.  
Understanding VLT - Visible Light Transmission:  Visible Light Transmission is the amount of light that is let through the lens, the lower  the VLT percentage the better  the performance in bright conditions by blocking more light , a high VLT percentage lets more light through the lens improving your optical clarity in low light conditions.

Sunny Condition Lens Tints

• Dark Smoke 8% VLT

Cloudy Low LIght Condition Lens 

• Amber 55% VLT
• Clear 85% VLT

Brand information: For Over a decade Anon Optics has challenged the competition by pushing the limits of design, style and technical execution. Inspired by the demands of the most elite athletes, Anon Optics design concepts ensure that every Anon product delivers un paralleled performance while giving the skier or rider the ability to make their own style statement.  When you purchase a pair of Anon Goggles, you can rest assure you are getting a industry leading product that has the performance & style that you are looking for.
About ASO: At Action Sport Optics we are leaders in sport & lifestyle optics with over 20 years of industry experience. We pride ourselves in great products from the leading brands, superior customer service, product knowledge & fast shipping. Eyewear is our vision!