Beslands Hole Gauge Set, 1/8" to 1/2" Range, Telescoping Bore Gauge, Ball Type Small Telescopic Gage, 4 Pcs Full Round, inch/mm, High Precision (1/8" to 1/2")

These work OK for measuring the diameter of holes at various depths. Use of any such telescoping bore gauge tools is a tricky procedure and requires some "feel", trial & error, etc. to produce reliable results. Given that caveat, this set is a good choice for someone like me that only needs them once in a while.

These are great as long as you are not using them to build a rocket for NASA. Some of the tools are a little "rough" initially but seem to smooth out just using them. Works great for garage mechanics.

I bought this set to measure my rifle bore diameter. It was easy to use.

I needed a way to check the dimensions of holes and these telescoping gauges are the answer

These do a great job and are very affordable. Highly recommended.

Measures inside an engine cylinder bore. Very reasonably priced. Several different sizes to measure different things.

Like at least one or two other reviewers stated about these cheap instruments, it is a crap shoot. . . Since a couple of them were sticky at first.. . But I carefully worked them back and forth a few times and they got much better. . . Be sure to store these properly, and unless you got a lemon, they should last the average Home owner/mechanic, machinist or whatever for many years, I am guessing. I have not used them yet, but I think they will work decently. . . Hey, IF you want super great perfection, quality; then buy one of the expensive top quality brands. . And IF you are a full time machinist, maybe that is what you should do. I wished I had them a week ago, when I had to measure inside my truck rear end, instead of trying to concoct something on the spot to get me by. . .I would not be afraid of buying this again, IF that changes, I will let you know. . .but know this I will be 80 in a few weeks, and my avid wrenching, etc., are about done now. Good bye.

This bore gauge set will be difficult to use and may damage the inner surface of the bore being measured. The general way that a bore gauge works is that there are two telescoping gauging rods which extend out of either side of a central fixture which is attached to the end of a handle. At the end, the handle has a rotating grip which can lock the rods in place when it is turned. The rods are pushed out to their maximum extension by a spring when the grip is twisted and the lock is released. To use the gauge, you lock the rods at a slightly smaller diameter than the bore being measured, and put the gauge into the bore. Release the lock and the rods will extend until they reach the bore surface being measured. Try to hold the gauge so the handle is as parallel to the bore surface as possible, and adjust the lock so there is just enough friction to hold the rods in place but not hold them solidly. Then rock the gauge handle back and forth very gently. As you rock the gauge, it will pass the point where it is exactly perpendicular to the bore. At that point the rods will be pushed in to exactly the diameter of the bore, and the gauge rods will be at that length. The lock adjustment will hold them in place . Tip the gauge slightly and tighten the lock adjustment to hold the length, and remove the gauge from the bore and measure with a caliper or micrometer to find the exact bore diameter. In order for this measurement to be accurate, the two rods must slide extremely smoothly in and out as the gauge is being rocked in the bore. If they stick or bind as they extend or retract, the diameter measurement will not be correct, and the bore may be scratched. Starret or Mitutoyo gauges have very finely polished rods which slide smoothly in and out, pushed by a finely calibrated spring. This polishing is time consuming and expensive to do, and fine measuring tools are expensive. The smooth action is necessary to provide accurate measure of the bore. This gauge set looks like a quality tool , but the rods do not slide smoothly, and won't follow the bore surface well. They will not provide accurate measurements and may scratch the bore surface. There are many cases when a Chinese tool which is reasonably close to the quality of a fine tool will work to get the job done, and will be good enough to use to get the job done to a moderate quality standard, if you use extra care. This is not true of precision measuring tools, and you are wasting your money to buy something like this.Better to borrow or rent a good gauging set, or buy a used product from a respectable manufacturer in good condition. You will spend a lot of time fiddling with this gauge set, and you cannot be sure the result is accurate or repeatable.