The box contains 6 layers of foam arranged as follows from bottom to top:
A-B-B-B-B-A where A is 1.5" thick regular open-cell foam while B is 3" thick Pick 'N' Pluck open-cell foam. Both A layers have small cut-outs to accomodate the case's wheels and one of its handles. The B layers have no cut-outs.
The advantage of the Pick 'N' Pluck foam is easy customization without tools. However, I plan on upgrading to customized foam inserts as discussed at ar15.com.
Pros: sturdy
Cons: heavy
This review was written in the old system and had content requirements that are different than reviews written today.