Since you also have to buy machine screws, they are a little expensive at $0.15 each, in quantities of 100. These brass inserts perform better than expected. The soldering iron tip makes them incredibly easy to install and the holding strength is more than sufficient for anything you would be 3D printing in plastic.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.
These work best if you put some material between the threaded insert and the part your bolting up to. So, rather than inserting your bolt like the one in the picture, insert it from the opposite side of the block. This reduces the chances that the insert will simply pull out. Instead, it forces the bolt to pull the insert through the part, which is much more unlikely. It’s a little more work up front (drill the insert hole, and a through hole) but well worth it.