A trailer should always have a positive nose load. A jockey wheel is there to provide support for this load when the trailer is uncoupled and also help maneuverability when manually moving the trailer. The 3500KG refers to the maximum weight capacity in which this jockey wheel can withstand, from the weight of the trailer. Meaning that you can use these jockey wheels on a trailer up to 3500KG in Gross Weight. The telescopic jockey wheel will save your back while uncoupling because the winding facility takes the load off yourself.