This is a modded version of another radiator cover and a voltmeter that was posted a while back. The optic has always needed a good place for a voltmeter, this makes it easily visible from the rear of the rig. Attaches with 4 screws from underneath, and the voltmeter screws in from the rear with (2) 4-40 x 3/8" screws. I wired a plug to mine and plugged into my RX and monitor voltage there. 

The voltmeters can be found on amazon. 

https://www.amazon.com/dp/B0BL6QL573/ref=sspa_dk_detail_0?psc=1&pd_rd_i=B0BL6QL573&pd_rd_w=JRLft&content-id=amzn1.sym.8c2f9165-8e93-42a1-8313-73d3809141a2&pf_rd_p=8c2f9165-8e93-42a1-8313-73d3809141a2&pf_rd_r=4VAB5G2SP351R7PFN5MK&pd_rd_wg=e7o5X&pd_rd_r=c27ab426-17f7-4d7b-9197-0bf3a20c8bad&s=industrial&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw