The 3510 foam kit is made of two pieces, a large piece of pick-and-pluck foam that is designed to allow the customer to customize the foam to specifically fit an object of the customer's choosing. There is also a thiner layer of foam that is just intended to be a protective layer at the bottom of the case. The large piece of pick-and pluck foam = 7.75" x 3.75" x 2". Each individual tiny cube of the pick-and-pluck foam = 3/8" x 3/8" x 2".  
The small piece of foam that lines the bottom of the case of the OtterBox 3510 = 7.75" x 3.75" x 0.5".