We often get asked "what's the difference between the Zeta 4 and the Zieg 4?"

Well, couple things...
1. The Zieg 4 has a more upright seating position when the seats are standing up straight.  Great for guys who need to recline their seats.

2.  The Zieg 4 has a more narrow shoulder bolster, which allows for easier fitment in roadsters or small vehicles.

Now that's been explained, we also get asked "how much wider is the wide version?"
We took some physical measurements, and the Wide version is about 1.5" wider in the critical areas.  
I'm a 33" waist pants size, and I fit in the Zeta 4 comfortably.  You could squeeze in a 34" waist, and it's snug.
The Wide version - I could put my hand between the thigh supports.  
The holes for the harness is also higher then the standard version as well.
Wide seats can easily fit up to 36" waist size.