Tucked away inside another building, so you have to know it's here and cross through the lobby. Extensive selection glass and mirror, from thin to thick and bevelled.
They take their work very seriously - like craftsmen. I took in an empty frame to have them to cut and install a mirror. They did a good, careful job. The owner came out to inspect what his underling had done and to make it perfect.
They might make you a deal if you become a regular - I've had several mirrors cut here. They have charged $40-50 for a medium-sized rectangular mirror. Their hours are not very convenient for NYC - partly because they are inside that other building, rather than with a storefront.