It says 3" in diameter. Unless they're getting American jars, it's unlikely that it'll fit. Theirs are probably metric, and may have a different screw. OTOH, it's hard to tell from the picture. If the lid is silicone (soft) sided, then it should fit any jar that's close enough. They sell Italian canning jars here that are about 3".

They are metal screw on lids. We have them on typical mason ball jars.

The chances are that they won't fit. I found a case of quart Ball jars on Amazon.it Marketplace, so there are some in Italy, but they're at a truly prohibitive price (367,34 EUR, or about $35 per jar!). These look like they have two part lids, but I couldn't find a listing for seals. The vendor probably does have them (not that the purpose here is canning). I'd guess that they wouldn't fit Bormioli Rocco ($3.86 - 5.10) or similar Italian jars. They have a similar product, jar included: http://www.amazon.it/Front-Runner-Consol-Solar-Light/dp/B00ZUMHWG8/ref=sr_1_cc_2?s=aps&ie=UTF8&qid=1440187645&sr=1-2-catcorr&keywords=solar+jar+light My Italian is really repurposed, moderately decent Mexican Spanish, so I'm about at my limit here.

You might try e-mailing the manufacturer, or perhaps call this store: http://www.tinntreasures.com/Angel-Tears-Solar-Lid-light-p/360319.htm

3" is 76.2mms. I have Italian jars and the lids are all marked in mms and the closest I have is 86mms so I'm guessing it won't fit.