Reticulated foam is a very porous, low density solid foam. 'Reticulated' means like a net. Reticulated foams are extremely open foams i.e. there are few, if any, intact bubbles or cell windows. In contrast, the foam formed by soap bubbles is composed solely of intact (fully enclosed) bubbles.
All the outdoor foam we use is a 1.75-1.85 density. This is one of the important factors of foam performance for comfort, support and durability. It's also a main factor of the cost of the foam. Foam density is not really weight, it's actually a measurement of mass per unit volume for a cubic foot of filling.
All of the filling that we use is 21-29 lb firmness or IFD. The larger the number is, the firmer the foam will feel.