The laser cover is an excellent way to improve the thermal stability of the laser by shielding it from the air drafts that can otherwise cause small shifts in plate and device temperature. For applications that require the highest level of temperature stability, the 200-C cover is an excellent addition. The cover works with the 203, 205, and 207 mounts, and can also be used inconjunction with the 200-TRAY fiber management tray. The cover can be screwed down or simply set onto the mount... alignment pins built into the cover will prevent it from sliding around.