What is the difference for the full ball wheel and Retainer wheel of your X348,X458,X678 trolley?

What is the difference for the full ball wheel and Retainer wheel of your X348,X458,X678 trolley?

OurX348,X458,X678 trolley wheel with full ball type is preferred for dirty, gritty, moisture laden environments.

OurX348,X458,X678 trolley wheel with Retainer type is providing the lowest friction and reducing the conveyor drive energy and size requirement.