Barlow Lens 2.5x 3-element 1.25"

My comments are based on using it with a 102mm ED refractor, FL 714 mm. My home is in a Bortle 5 location in Christchurch.
This shorty Barlow is an apochromatic design, it uses a brass compression ring and is light at approx.100gms. I've used it several times in mostly poor viewing conditions, and once in above average conditions. In that time I viewed double stars, emission nebulae, open and globular star clusters, and Jupiter. I thought it provided excellent views and on the one occasion when seeing conditions and the city lights were less in the early morning, I was able to achieve 203 x magnification looking at a globular while still getting a reasonable view. Even at 238 x the view was tolerable, albeit quite soft.
I also have a Celestron X-Cel-LX 2X Barlow, so was able to compare the two Barlows. I found them pretty much identical in terms of colour, sharpness and contrast, though someone with better eyesight may notice differences that I can't.
I highly recommend the Astronz 2.5X Barlow, as it can provide substantially higher magnification options if you have, say 3 or 4 eyepieces. Personally, I prefer my 2 X Barlow as its more useful in less than average viewing conditions, which for me is most of the time. However, in above average to excellent viewing conditions, or at a dark sky site, the extra magnification of the 2.5 X Barlow would be very useful. If you are just starting out and wanting to get a Barlow, the Astronz one costs $48 cf. $249 for the Celestron. The choice is pretty much a no-brainer from that perspective.
I'll continue to use both, as different EP combinations and magnification steps will suit different viewing conditions.

Barlow work best with the superview and extraflat astronz eyepiece, we tried to paired it with standard ng eyepiece, for eye observation, it still consider good E.G: we can clearly see the ring of saturn and the gap to the sphere in a decent size with combination 10mm ng with 25mm extender tube and 2.5x 3 elements Astronz barlow.
Terrestrial seeing with the combination of the above Astronz eyepiece, extender tube and eyepiece can get close magnification and help reducing the achromatic effect of the original colour of the object quite noticeable given conditions during summer. Eg. Aiming to the top cone of 30 m tall kauri tree from 60 m distance, we can see the scale opening pretty obvious. (We did not use any filter). We are also found It does works well with the iphone pro series as we were taking life photos and video with the help of the mobile mount and managed to get the best shoot of the frame in a decent quality.

Bottom point: Astronz product added value to the scope as we can push the scope to its limit, which if we relying its original accessories, pretty much nearly impossible to achieved.