The shorty leg extensions are 9†long (compared to 18â€). They were specifically designed to be used with the 2†sight glass in the vertical arrangement. This was the major design criteria that Engineering noticed.
The long leg extensions were specifically designed to bring the racking port to a height where the conical can be gravity drained into a 5 gallon corny keg. However they are pretty long for those people that do not need to gravity transfer but want the conical high to use a sight glass for example.