Teflon sealing ring question

Just finishing up a rebuild on my late 80,s 904.
I purchased a Teflon sealing ring kit from A&A trans and I have noticed that the thickness
Or the width of all the rings in the kit a significantly thinner that the metal ones I took out. Do I have the wrong year or is this normal for the Teflon ones to be thinner.
Cannot say that I recall seeing this before and the A&A catalog seems confusing.
The diameters look right, just not the width.
Can anyone shed some light.
Thanks

Duane