LoneRangeFinder Loc: Left field

These are made in +1, +2, & +3 increments. They thread into the front of a lens like a filter and are mad3 of Schott glass. Does anyone know how much each of these increase magnification?

dpullum Loc: Tampa Florida

The subject of Schott glass is a different discussion from how much magnification... that answer depends as discussed and has a calculator:
https://www.cambridgeincolour.com/tutorials/macro-extension-tubes-closeup.htm

While the title says extension tubes... the articles also discusses closeup addon lenses. The 1, 2, 3 are diopters and not direct magnification numbers as noted by the addition of a calculator.. it depends on focal length of the lens...."For example, a 50 mm lens requires +10 diopters to achieve a magnification gain of just 0.5X, whereas a 200 mm lens requires only +2.5 diopters."

Mark Sturtevant Loc: Grand Blanc, MI

I have never heard of them, but have learned a couple basic things just now. These are two-element lenses, which is good since that suggests they include a degree of optical correction as they magnify. Single element diopters are notorious for distortion around the periphery. The Heliopan lenses are also a tad pricey, but that suggest quality as well since once does tend to get what you pay for.
I had not found reviews on these, but Johan J Ingles-Le Nobel, who is very knowledgeable, lists them as recommended. You can see info here: http://extreme-macro.co.uk/extreme-macro-closeup-lenses/ He seems to favor Raynox lenses, as do I. An advantage there is that the Raynox system uses a spring-loaded clamp rather than a threaded mount, so adding and removing them is much faster and they can be put onto lenses of different filter sizes.

LoneRangeFinder Loc: Left field

Thanks, Mark. I know of Johan J Ingles-Le Nobel and have his site bookmarked. I had neglected to look there—so my bad. He has some excellent resources and does fine work. Occasionally he posts on here as Nass.

I will try my Raynox first. I looked a lot for dual element diopters but haven’t located a source for the size I was looking for. I wanted to avoid stacking stepup rings. Heliopans have a good reputation—but they are special order and are non returnable.