Hoya RM100

The 50x50 size fits perfectly into my filter holder, and cutting through infrared glare is exactly what I needed for landscape shots. Took a few test frames to dial in the exposure, but the results are crisp and worth the fiddling.

Ordered the 50x50mm square to use over my camera lens for some IR shooting and it drops right into my filter holder with no wobble at the edges. Glass looks clean and evenly polished, no visible bubbles or coating haze, which matters when you're stacking it in front of a hot mirror.

The 3mm thickness feels solid and well-made, and the 50x50 size fits perfectly into my filter holder. Infrared shots come through with no hotspots.