This tool set consist of a brass heat set tip adaptor and 7pcs of tip heads for soldering irons that uses 900M T18 ST soldering tips such as FX888D WLC100 SP40NUS Milwaukee M12 Radio Shack 64-053 Yihua 926 Yihua 939D Ryobi P3100 X-Tronic 3020 series Aoyue 9378 Aoyue937 + soldering tools or any irons that fit a OD.1/4"(6.35mm) I.D .16"(4mm),barrel length approx. 1"(26mm)tip.with this tool set it is very easy to install heat set insert to your 3D printing parts,more importantly,it won't ruin or contaminate your part as it offten happens when you are using a normal soldering iron tip that either stuck or penatrate the insert hole. There are 7 different tip heads for M2 M2.5 M3 M4 M5 m6 m8 heat-set inserts and it is very easy to change the tip head,it is no need to take off the whole soldering tip,just screw off the tip head and srew on a new one.