i dont know

that would make sense to me too... i also don't like the idea of foam in my tank.. plus not being able to pull the cap off and see exactly how much fuel you have at a glance..
 
well, from personal experience. anything that claims that it is made from "military grade" anything is not worth the $$$. here is why:

the military buys things from teh lowest bidder. lowest bidder means lowest quality that they can get by with while staying in a specific set of guidelines for weight and dimentions. they type of material used is always left up to the manufacturer and is usually the cheapest most flimsy substance they can use to meet those minimum standards. i know this because i have spent the last 12 years of my life dealing with the overpriced garbage that we are expected to work with.

now, in my opinion of this, its a great idea and is actually proven to work. i have seen it used many times in sportbikes that are set up for the track where 5 gallons+ of fuel is quite violent when it sloshed around between your legs at full tilt. while i have seen many diffrent types of these used, the cheaper ones are usually the ones that disolve in the fuel and cause major issues down the road. if you use one, be sure its a name brand version made from top notch foam or you will end up replacing your motor.