These very smart sunglasses feature Spectron X5 or Alti Spectron X6 Polycarbonate Lenses, which are recommended for all sports because of their shock-resistant and lightweight qualities.
They are Cat. 3 (X5), transmitting 8-18% visible light, or Cat. 4 (X6), transmitting 3-8% visible light, and suitable for bright light, mountain and water environments.