These brass threaded heat set inserts are very helpful when you need to add threads to plastic molds or 3D printed parts, these inserts featured a tapered end which made it much easier to insert it into the plastic parts, just heating up your soldering iron at around 392℉（200 ℃）,wait for a few seconds till the plastic flow around the insert then push it in with a little pressure, press it for a few seconds then it is done.