Hydraulic spindles

Go to kenoconnorracing.com

They're on the OEM blaster parts page
 
Those look nice and would probably be better then finding a used set. My only question is that he has 2 different listings 1. Blaster hydro conversion spindles $165 2. Blaster hydro conversion spindles with good core exchange $135. What is the difference between the two and which one would I need? I can always call up Ken too!
 
The core exchange means you send your spindles in to him. He keeps them, and in return you get new spindles and a discounted price. Just like when you get a new car battery.
 
Buy the complete setup that jbuck has in the for sale section and have a bunch of stuff left over for spares.