Check the listing for details. BUILD YOUR OWN SPECTROMETER W/ B&W Tek BW BWTEK PARTS - GRATING & MIRRORS - DIY. Condition: Used. Listed at 79.99 USD. Up for sale is my B&W Tek grating and mirror set complete with their mounts. You get the three pieces you see in the 1st picture which is a B&W Tek grating, a B&W Tek collimating mirror, and a B&W Tek focusing mirror. These three pieces came straight out of a working spectrometer so they are without defects and will be shipped to you in a way as to not scratch any of the surfaces. The grating is 1800 Gr/mm with a blaze wavelength of 500nm. One thing I especially like about this set is that the focusing mirror comes with adjusting screws so it is much easier to align the optics once everything is mounted. The graph in the last picture is an efficiency curve of what one can roughly expect out of this grating. Thank you. I have been an eBay member since 2001 with excellent positive feedback. If you have any questions please scroll up and click "contact seller". Thank you.