The rail and carriage is Not interchangeable, so the 440C SUS carriage is Not sold separately.
When you purchase the linear rails, it is best to choose the original manufacturer of rails and carriages.
If you want to increase the carriage, it is best not to buy the carriage separately and purchase the factory customization.
It may be that your requirements are relatively low, and the purchased carriages are just right.
If your requirements are relatively high, be sure to purchase the original rails and carriages.