Quality differences in 20mm lenses?

Lasers
1

In the K40laser.se article Upgrades & improvements on the K40 laser cutter engraver it says: “When delivered, most of the machines has the cheapest availible mirrors and lens installed. Changing this up will gain you a lot. […] Read more about mirrors and lenses here”

However when I click on here, I get pointed to an article solely talking about different mirror types. With mirrors, I understand that there are quality differences already based on materials. However, all lenses seem to be made of Zinc selenide (ZnSe). Are there noticeable quality differences? How do I tell which lenses are good?

I’m based in Hong Kong, and my source is Taobao, an online market place for Chinese products. Normally shipment takes just a few days.

2

The quality of lenses is defined by the material pureness and the accurcy of the shape. Unfortunately both of them can not be seen by eye.

3

Thanks. It’s at least valuable information to know that there are indeed quality differences! I found that some shops on Taobao offer imported and domestic lenses. The imported ones are more expensive.

Examples (D = 20mm, f = 50.8mm):