Lens materials
MR-8
Optical glossaryLens materials
The tough mid-index material of CLIFF's 1.60 lenses — impact-resistant enough for drilled rimless mounting and the range's breakage warranty.
Illustrative · the shape of the principle, not measured data
In more depth
MR-8 is a thiourethane lens monomer made by Mitsui Chemicals. It sits at a useful middle point: thinner than a standard 1.50 lens, with better color performance than the highest indices, and tough enough to be drilled.
Drilling matters for rimless and semi-rimless frames, where there is no rim to hold the lens and the screws pass through the lens itself. A brittle material can crack at the holes; MR-8's toughness is why rimless mounting in the CLIFF range is made at 1.60 or above.
Across the CLIFF index range
| Index | Material | Curve depth | Reflection | Abbe |
|---|---|---|---|---|
| 1.60 | MR-8 | 83% | 5.3% | 41–42 |
Curve depth is relative to a 1.50 lens of the same power, and reflection is for one bare, uncoated surface — both calculated from the index itself. Material and Abbe number are the material manufacturers' published figures, not CLIFF measurements.