The Fortis Finseeker Amber Switch Green Xblok Polarised Sunglasses (FSG004) build on the success of the brand's first glass lens model, the FSG003, with a new variant focused on depth perception. By pairing the same photochromic amber glass lens with a green mirror, these sunglasses heighten the angler's ability to judge how far off the bottom a fish is sitting. This makes them especially useful when targeting deep, clear water, and they have been much requested by the bass fishing fraternity. Glass lenses offer a range of advantages, including clarity, scratch resistance, and polarisation. These Italian glass lenses incorporate Fortis SWITCH technology, meaning they change colour and shade when exposed to UV light. In bright conditions the lenses darken, while in low light they lighten, giving the wearer perfect vision throughout a session, whether fishing at dawn, stalking in the midday sun, or looking for subtle signs of fish at dusk. - Weight: 41.7g - VLT = 15-30% VLT stands for Visible Light Transmission and measures the amount of light that reaches your eyes through your lenses. It is measured as a percentage which indicates the darkness of a lens: the lower the VLT, the darker the lens. VLT is affected by the colour and thickness of the lenses, the material they are made of, and the coatings they have on them. Fortis provides a rating on each model to help you choose more wisely. When choosing between glass and polymer lenses, each material has its pros and cons. Glass offers 100% polarisation, unrivalled optical clarity, richer tones, and better scratch resistance. Polymer lenses are lighter in weight, making them more comfortable for long use, and are more cost effective to manufacture, offering a more affordable option without significant compromise to performance.