Makita Toolbox Multilayer Foam Inserts. Makita Makpac Foam Insert. Multilayer Foam foam is an infinitely customizable foam insert that allows you to easily create your unique Milwaukee toolbox insert. Don't let your expensive tools roll around inside the toolbox, fill it with Multilayer Foam. Multilayer Foam (MLF) is made from Polyethylene which is the same material that companies use to make precision cut foam inserts using commercial CNC or waterjet equipment. Polyethylene is a dense material which means the foam is extremely durable and long lasting compared to other foams and provides far greater shock absorption to keep your equipment safe. Polyethylene is also “closed cell” which means it is waterproof and not impacted by humidity or moisture..