The Pulsar Engineering Community Board

Hello,
Recently I've built the Performance Edition Raman Spectrometer and I have a question - what is the point of this part - 2020-20_1 - TO92 HESTSINK? I don't see it being mentioned anywhere, but it was in the download files. I have attached the jpg of this part.

It's for the custom TEC/LD driver you don't need it if you use a different driver/off the shelf one.