The Alleycat/Kingpin lens ratings are as follows:
Low-Light = S0 (86% VLT)
Amber = S2 (29% VLT)
Violet Chrome = S2 (25% VLT)
Red Chrome = S2 (28% VLT)
Silver Chrome = S3 (19% VLT)
Smoke = S3 (19% VLT)
The higher the category (and lower the VLT %) the more light the lens blocks, so an S2 lens is often good for if you're riding in varying light conditions, whilst and S3 lens will perform best if you're mostly riding bright conditions. We've also released a more in depth video on the lenses, which you can check out here: https://melonoptics.com/alleycat-lens-tech/
You can also check out our Facebook group which is a great space to interact with some of our customers / team members and ask questions too. Just follow this link.