The Jimny Coil spacer is made to cup the upper mount of the body and conform to the spring, it is designed to do this so it fits the front and back. While the front has the bump stop inside the spring to help locate it, the rear is in a different location so the spacer locates the spring so it does not move out
Coil spacers are are great way of changing the suspension hieghts with out changing the ride of your vehicle
Note for new players: when adding spacers the shock travel can be made to short depending on your set up, so its somtimes best to add new shocks or shock spacers