This is a terrific product once you figure out how to assemble and operate it without instructions.

You will get it with 3 small watch/hearing-aid style batteries. Screw apart the illuminator in the middle. The batteries go into the half with the clear plastic tube that has a small round battery contact inside. The batteries go button side down, flat side up, into the tube. Stack all 3 batteries the same way, then screw the other half of the illuminator back on. You should be able to see the red light come on at the end of the illuminator when you click the switch knob on and turn it all the way bright.

Screw the illuminator into the hole in the side of the eyepiece. Turn off the illuminator light and look through the eyepiece in normal room or day light and see the four black crosshairs. Most likely they will be very blurred. The ring on top of the eyepiece is for focusing the cross-hairs, so turn it as many turns as needed to get the two double cross hairs into sharp focus, and you're done. When using it at night through your scope, adjust the illuminator brightness as needed, depending on how bright your target is.

On "first light" with this eyepiece, I achieved the best alignment that I've ever experienced with my Alt-Az mount.

This makes centering objects very easy when trying to photograph them using neximage camera. A real time saver. Simply center the object in the crosshairs and it is centered and visible on the cameras view. Also good for auto aligning celestron telescopes.

I bought this to align a red dot finder with my Cassegrain telescope. I located a distant object and used a succession of eyepieces finally stopping with this one, which has a lens focuser. The crosshairs glow red when lit, but for daytime alignment, the black crosshairs were perfect with illuminator off. Knowing the exact center ov my field of view made aligning the red dot to the same distant object a breeze. Recommended.

Product itself was exactly what I was expecting, thankfully it was well packaged since the driver thew it over the gate at night in the rain. The eyepiece was internally packaged in waterproof materials so it was thankfully undamaged.

Works as advertised. The crosshairs light up nice and it seems very accurate. I like the dimming feature and there is a "focus" adjustment to bring the crosshairs into good focus. I wish the battery pack/switch was smaller.
Overall good product at a reasonable price. I could spend more and probably get something better but being an armatures armature I try to keep things cheap.