This is amazingly good after being totally disappointed with the Harbr Freit version for looking inside walls. The 8mm tip slips easily through a 3/8 hole, and with its rim screwed off can just fit in a 1/4" hole. I can make a view hole outside a switch box but will still be covered by the wall plate. I got the dual-lens, and the side view lens is the most useful one inside a wall. Even with no focus or autofocus, I can see well enough from close up to at least 2 feet. The LED is plenty bright and can be dimmed for close work. One weird quirk is that the image is 90 degrees rotated from the tip, which makes it very hard at first to tell right from left, and which inside of the wall is closer to you vs farther away, and it's not intuitive which way to turn the scope while viewing. The Rotate button will flip the image 180 degrees, but not 90 degrees.This solves stud finder problems and more. I have mortar on perf-board walls (like plaster & lath), and all my stud finders fail miserably, including the wall robot Plus that attaches to a phone. Miserably. But this scope shows me approximately where the studs are, and discovered how deep the stud space is, and showed me a 2" pipe next to a half-inch pipe, and how many electric wires, where they are, and whether they are stapled to studs; so I can avoid drilling or opening the wall in the wrong place.