Materials Hard Resin Index 1.498 Material Index Abbe Value Specific Gravity 1.498 59.0 1.32 Mid Index Material N-157 Material Index Abbe Value Specific Gravity 1.566 38.0 1.18 Photo Chromatic Mid Index Material PH-156 Material Index Abbe Value Specific Gravity 1.5562 36.6 1.19 Colours                : Grey and Brown Fashion Colours: Blue, Purple, Magenta, Green, Orange, Red, Yellow