I researched this company "Depstech" before buying, as I'm wary of Ch*nese companies, but the reviews and TrustPilot were both good.I got the single lens DS520, and an extra probe with the 3-lens setup. This endoscope does exactly what you'd want it to, and I'm really happy with the build quality.The probe itself is detachable and can be interchanged between the 1-, 2-, and 3-lens probes, or probes of different lengths, available separately. The probe connects easily using USB-A, and the connector seems to be holding firmly. This functionality of using any DS520 monitor with any DS520 probe is excellent, and really increases the value for me, as if one part fails, it's not useless, and being able to remove the probe/cable for storage and transport takes the strain off the end of the cable, where it connects to the device. Permanently-attached cables are just trouble, they can easily get damaged from being strained, and once they are damaged the whole device is useless (not an issue here!).The probe wire/cable (it's all one piece, the probe and cable) has just about the right amount of stiffness to be easily formed to go where I want it to aim, but can also be easily straightened or coiled up for storage. It can be inserted quite far, and doesn't collapse on itself. Unlike some models (eg Ridgid), this has a smooth cable sheath, like THHN wire, and won't abraid or snag on objects. The probe portion at the tip comes with a protective lens already attached, which makes the end slightly larger than 0.25" diameter. It's removable (not easily!) and there's a hook, right-angle mirror, and a magnet attachment included in the kit. For mine, the right-angle mirror still had the blue protective plastic film attached, which is a minor nuisance to remove. These come in a little capsule that has a spot to be stowed in the included storage case. The end of the probe has a non-flexible portion housing the camera/electronics that's about 1.25" long. If you want to insert it into an opening already bent at a right angle, it'll need about 2.5" of bend radius.The storage case is the semi-rigid type, and has the perfect layout for storing 1-2 probes, the monitor, the accessories capsule (or two), and the USB-C cable, as well as the instruction manual. The case is really good, and is no larger than necessary, wasting no space.As for the monitor, it does exactly what's needed. It's fairly light weight, but it doesn't feel poorly made (I'm glad they didn't add lead weights to make it "feel more quality" like some companies do). There's a hump on the rear and some texture to get a better grip. The screen is really flush with the front of the device, I wouldn't expect it to stand up to many drops or abuse, but if you use it properly it should be fine. On the top is the USB-A port for connecting the probe, and the bottom has a USB-C port for charging and data transfer. Thank you for being type-C instead of micro-B! There's also a slot with a pre-inserted microSD card (32GB). The monitor will only stand up in landscape mode, it falls over in portrait mode.The software works fine, it's worth reading the manual for 2 minutes and it easy to figure out things with a few button clicks. One review here claimed that "you can't access photos or videos on-device, only on a computer from the SD card or type-C cable", and this is simply false. The photos and videos you take can be accessed by holding "OK" for 2 seconds, it's in the manual in two different spots.As for the picture quality, it looks about the same as a Ridgid or Klein borescope. There's plenty of information and clarity in the picture, and you can rotate the display and change the brightness of the camera light on-the-fly to get a better image. It's worth noting there's a small but noticeable lag from moving the probe to the image on screen, it's around 1/3 second. The image quality is good enough to read text on a screen from 1-2 feet away, and within its focal range, it's enough to see the detail in my fingerprint.From pressing the ON button to being ready to use the device is less than 5 seconds.I haven't used the device for long enough to accurately say how the battery life will be, it's 3-4 hours advertised.The probe claims IP67 waterproofing rating. I haven't tested this, but assuming it's in good condition, it seems likely it'd have no issues in water. The monitor is NOT waterproof, just the cable and probe.I don't usually do reviews, but at the price I paid of $55, the quality and value here is outstanding. I will update this review if there are any issues with the borescope in the future.