What is a good step viewer ?

What is a good step viewer that allows viewing without first converting the step ??
And allows measurement.
Preferably some kind of freeware.
The purpose is to enable all participants in a project to view steps, even if they don't have any CAD application installed at their own site.
The challenge here lays in the following:
Though most applications do allow you to view a STP file,
Almost all cannot open, but need to import a STP file.
Importing entails converting the file to the apps native format.
Such conversion takes time, and creates a lot of unwanted files.
So
What I am looking for is an app that can open and show a STP model, without the need for import/conversion.
Same for the STL by the way....