One of the simplest innovations in Transformers toys, using universally sized posts for accessories, weapons and figures is something that has characterised several Transformers lines throughout the years. The most common universal post and port size is the 5 millimetre (5 mm) post (also commonly stylized without a space as 5mm post in defiance of SI standards). This size was used throughout Generation 1, Generation 2, and almost universally throughout Armada, Energon, and Cybertron.

Using a single, universal size of weapon post allows Transformers toys to swap weapons between one another. During most Transformers toy lines, this interchangeability was seldom advertised as a feature of the toys, but during Armada, that changed. The introduction of the Mini-Cons gave 5 mm posts an entirely new purpose: A hollow 5 mm post could now become a mounting point for a Mini-Con. The interchangeability suddenly became an advertised feature of the toys.

The 5 mm post has become pretty ubiquitous in Transformers toy design, with only a few lines (mainly the 2007 live-action movie and Animated) favoring less-interchangeable systems