Schott RG9

The 550nm cut-on is exactly what I needed for my fluorescence setup, and the 3mm thickness makes it easy to handle without worrying about breakage. Arrived well-packed and clean.

The 3mm thickness feels solid in the mount without adding much weight, and it cuts the visible band cleanly while still passing the near-IR I need for my camera setup. Edges were clean and uncoated, no chips. Exactly the longpass curve I was after.

Picked this up to block visible light in my IR setup and it does exactly that, sharp cutoff with barely any leakage. The 3mm thickness feels solid in the mount and the edges were clean enough that I didn't have to fight it into the holder.