Captive Ball Cars are smooth running, efficient and easier to load and unload from CB track Used with 1631 or E2730 for 3:1 purchase Recirculating ball bearing travelers move freely under non-vertical loads and have a low-profile design The fully machined bearing races provide smooth operation and the captive bearing feature takes the hassle out of installation and maintenance The "old" 1500 Series Midrange cars will work on the new track but not the other way around