The 937 and 936 soldering stations can be used with three different soldering irons. The particular soldering iron determines the tip series. If the iron model number is 900S-ESD the tip series starts with 900S-T-xxx. The 907 model soldering iron uses 900M-T-xxx series tips and the 908 model iron uses 900L-T-xxx series tips. The most common soldering iron is the 907 model.

900S - Small 

900M - Medium 

900L - Large