Commercial Quality Windows, Square, Borofloat 33

The parallelism on these is the tightest I've seen at this price - my laser bounced back dead center without any shimming. Surface quality looks clean under a flashlight, no digs or sleeks anywhere. Took two weeks to arrive, but worth the wait.

I was worried about edge chips since I'm using these in a laser setup, but the edges came clean and the parallelism is dead on. The ±0.125 mm diameter tolerance held up when I measured them with calipers.

The surface quality is exactly what I needed for an optical setup—60-40 scratch-dig and zero visible defects on arrival. Parallelism came in well under the 15' spec, so my beam alignment stayed true without extra shimming.