This 90° 1.25" mirror-type star diagonal uses enhanced aluminum mirror coatings for a full 95% reflectivity. The mirror is overcoated with quartz for long life. The mirror housing and 1.25" barrels are precision-machined from a single block of solid aluminum, rather than being simply a pair of less-rigid tubes screwed into a flimsy plastic mirror housing or sheet metal stamping, as with lesse . . .