Hoya RM90

The 3mm thickness feels solid and well-made, and it cut exactly to the right diameter for my lens adapter without any chipping. Blocking visible light while passing infrared through this dense glass works perfectly for my experimental photography.

Picked up the 12.5mm diameter version for a small IR sensor build and the optical polish is flawless, no visible bubbles or coating haze at all. Blocks visible light exactly like I needed for the cutoff.

The 3mm thickness feels reassuringly solid, and it fits my filter holder without any wobble. Cleanly blocks visible light while passing infrared, so my test shots came out properly exposed.