The KM Innovation ZnSe datasheet lists available maximum size as Ø800 × 30 mm thickness. That is a plant limit, not a catalogue of every diameter we have on a shelf in Florida.
Area is the product
CVD grows a plate. We have photographed effective sheet areas in the 800 × 1200 mm and 800 × 1400 mm class. You nest blanks out of that area. You do not order “a little ZnSe” the way you order a glass disc from a drawer.
How to write size
Round: Ø × T in millimetres. Rectangular: L × W × T. If the part is SMTY, say whether the +2 mm oversize is already in the CAD. Core-drilled stock on this desk uses +2.032 mm on diameter and ±0.254 mm on thickness. A drawing beats a vibe. Domes and non-plano shapes need STEP or DXF.
What Ø800 does not mean
It does not mean every RFQ is an 800 mm window. It does not mean Florida holds that diameter as finished stock. It means the Gwangju CVD process is specified to that envelope. If you need a clear aperture near the top of that range, say so on the RFQ with grade, quantity and ship-to country. The quote will say what we can actually cut and when.