3X Explore Scientific Focal Extender; 1.25-inch Barrel; 4 Elements

a definite improvement over conventional 3 element barlows- less chromatic distortion and less coma at the periphery- excellent value as well.

I love every product this company makes you can't go wrong for the price

Nice optics, combined with a nice tightening screw that pushes a C shaped piece of metal against the eyepiece to tighten it. The Barlow requires an extra 1/4 to 1/2 turn of out focus. The brain dead portion is the barrel that fits into either the scope or star diagonal. If your diagonal (like my Takahashi) uses a compression ring to hold an eyepiece or Barlow in place, it likely will not tighten properly. The villain is the undercut on the barrel. It is quite deep, and very broad. It also tapers toward the bottom of the barrel. Thus, the Barlow has a floppy fit. The work-around? I used filament tape, or about a 4-5 filament width of the tape, and wrapped it around the barrel 4-5 times. <sarcasm>It looks really classy. Nice job, Explore Scientific.</sarcasm> Way to botch what should be a simple design. This comment likely applies to the 2x and 5x versions, as well.