If I am correct, it has to do with the length of the limbs. Kateras are their most parallel limbs and have smaller brace heights with the XT500 limbs. While others like the Pro Elite even offer options for the limbs, XT2000, XT3000, or the XT 3500 Limbs. And if you notice the brace height and the ATA gets larger.

ProElite
Use the table below to determine the correct specifications for various cam and limb options.





C2 Cam & 1/2
Cam & 1/2 Plus

Limb
XT3500
XT3000
XT2000
XT3500
XT3000
XT2000

Axle to Axle
42"
40.25"
37.5"
42.75"
41.375"
37.75"

Brace Height
9.25"
8.75"
8"
9.25"
8.625"
8.125"

Draw Weight
40-70#
40-70#
40-70#
40-70#
40-70#
40-70#

Draw Length
28.5"-34"
27"-33"
26"-33.5"
27"-34.5"
26"-34.5"
24.5"-33"

IBO Speed
290fps
300fps
305fps
283fps
295fps
300fps

You can find this info on their website. After selecting a bow, click on the "click for cam and limb options" and it will show what limbs it is available in and all the tech stuff. Other than length, I believe they are all the same. Hope this helps. I have the Katera and love it. It is very smooth, fast, and unbelievably quiet!