I bought a Romeo Zero Sight in July to mount on my P365XL; mounted easy -- shoots fairly well -- I need some more time to shoot to feel more comfortable. I brought the P365XL out last night to take shooting today. The Romeo Zero Red Dot would not come on, the trouble shooting guide that came with the instructions reads to change the battery. I called Sig Sauer Customer Service (CS) this morning, just to make sure, I didn’t miss anything -- The owners manual (instruction sheet included with sight) reads the battery last up to 10 Years -- I got 4 months. Sig CS told me over the phone if I have problems after the battery change -- They would send me a shipping label to repair my sight. Luckily the battery fixed the problem -- The Auto on and Auto off function seems to work -- but all you have to do is move the gun and the red dot energizes. Seems the Energizer Batteries seem the work the best for me -- The battery that came with the sight was a RENATA (Swiss made); but like the Sig CS representative said -- You don’t really know how long its been on the shelf prior to installing on the sight at the factory. Thought I would ask the forum, if anyone has any experience with the CR1632 batteries -- I read online some had really good luck with the Sony Batteries --and hit or miss with the Duracells.