Event for moving item into off-hand

@Mod.EventBusSubscriber(Dist.CLIENT)
public class AmethystEventHandler {
    @SubscribeEvent
    public static void onOffHandEquip( ??? ){

    }
}

What event can I use to capture the event when the player moves an item into their offhand AND event where they move it out of their off-hand

Trying to apply armour effects when a certain item is equipped