47:51 Best MightyLift Ultra FQU-11 Heavy Duty Mattress Center Support System, 3 Cross Rails, 2 Legs Each

The Mighty Lift is the easiest and most powerful solution for supporting today's heavier, super sized bedding. This best selling design is the ultimate support system for peace of mind. The Mighty Lift FQU series uses 3 Cross Supports with 2 Legs on each Cross Support.
The Mighty Lift system is for use on angle steel or wood side rails. Pre-drilled holes on the ends of the Cross Supports facilitate ease of installation and rigidity.
The Mighty Lift FQU Center Support System fits Full and Queen size beds. The C-clamp adjustment system allows for infinite width adjustment of the Cross Supports... continue reading »
Adjustable Width Range: 51-1/2" to 60". Adjustable Height Range (Floor to Boxspring): 7" to 11-13/16". Number of Support Rails: 3 Cross Rails. Number of Legs: 2 Legs Per Rail, 6 Legs Total.