CVI 1/4 waveplate for 825nm 1/2" dia.
CVI makes the zero order in 3 configurations. Air spaced in a ring mount, contacted in a ring mount or optically contacted. This one is the later and the fast axis flat edge is marked in orange, the slow axis black, though you can't see that in the photo.
These zero order plates have a wide wavelength tunability range of 80nm so will work well from 785nm to 865nm and have excellent temperature stability over other types.
They work well with 808nm as you can see in the photos. I placed one plate in a static mount and the other in a rotating mount to get them to function as a half wave plate for the photos.
These were chosen for Positive Light's Hurricane Ultra Fast laser
I combine ship to save on shipping.