Ha! I feel like a show host on QVC describing these. The 45mm means nothing to me when jewelry measurements are given; in inches, these measure about 1-3/4" in diameter, and 1/4" wide. The snap-bar closure snaps easily and is very secure. I believe these are electro-form: finished inside and out, but hollow on the inside so they weigh less on your ear. They aren't weightless, but I think I could wear these all day if the posts were more comfortable (my fault!--my holes are small) and my ears wouldn't hurt.

Here's what I mean by inside/outside:  When looking at the earring in your ear from the front view, the section facing outward is satin-finished with diamond cutting, behind that is highly-polished sterling. The backside of the earring is again highly-polished sterling, the inside part facing forward is multi-faceted diamond cutting.

My only complaint with these: My ear holes have become smaller over the years due to wearing thinner wires and leverbacks; the posts of this earring start out smaller where they snap into the V, but the posts taper off larger as you get to the part of the earring where it swings upward. So for me, the posts are slightly painful. If your holes are normal, you shouldn't have any problem wearing these - I've seen lots worse when it comes to sterling silver hoops. At least I can get these in!

These are much nicer in person than the Amazon picture, so I uploaded a photo.