Ultramount JR has the same beefy 3\16" thick steel construction as the standard Ultramount, however, JR is only 6" tall instead of 9 5/8". Footprint is 11.5" wide by 9" deep. Standard Ultramount plates cross over to Ultramount JR as well, so you can swap top plates if you choose to.
(Note) With Ultramount JR being only 6" tall, some press linkages will hang below the benchtop to impede opening of cabinet doors or drawers (If you have them) below your bench. If you have any doubt, before placing an order, measure the linkages hanging down below your bench top and subtract 6".
Top plates sold separately.