New-Old-Stock (sealed) - Oriel (Newport) 77218 Fixed Slit 120µm compatible with Cornerstone models 130/130B, 260/260B, MS260i and MS125  series monochromators and spectrographs. 

From Google AI-

The Oriel Newport 77218
is a precision fixed slit designed for use with Oriel monochromators and spectrographs. It is the most economical choice when a single, non-adjustable slit size is required for high accuracy and repeatability.

Specifications