Sure-Grip Junior King Pins Slotted Head SET OF FOUR  - with Jam Nuts When replacing or purchasing a Sure-Grip Junior King Pin, ensure that it corresponds to the size of the junior plate trucks (5/16") rather than adult pins. Each junior skate plate requires a single king pin per truck, so a complete set of skates will use four king pins in total. This matches the setup used for adult plates but at the appropriately smaller diameter for juniors.