Need a spare ArcLite Photochromic lens for you kit, or just to have in the vehicle when you need it. Here are the Ethos Photochromic Spare lens.
The P11 photochromic lens will vary the darkness of tint from 71% to 11% Visible Light Transmission (VLT), depending on the ambient conditions.
The P15 photochromic lens will vary from 80%-15% VLT.
The lighter (P15) and the darker (P11) versions of the photochromic lenses, are indistinguishable when they are in the un-activated (lighter) state, because there are some situations when you will need a lens that's as clear as possible.