On this group level we find all the terminals of a similar size that can therefore be grouped together. The main grouping variable is the size of the connection. We thus find all the 1,5-mm, 2,3-mm, 2,8-mm series, etc...

This grouping level is used to carry out the first classification in the catalogue, and gives rise to its different chapters, from the UP-MOD series to the special terminals series.