Best Acoustic Filling for Guitar Cab?

I've put sheets of insulation in cabs before with good results tightening the low end, but I've heard you can also just put some loose material in there, and my current cab has a closed back, so it's be nice to maybe just take one of the handle mounts off and pour some filing in there, but just wondering what people reccomend?

i know some people will say just empty a cheap pillow into it, etc, etc, but theres got to be a specific actual item/product that is best at this? yes/no/suggestions?

thanks.

take a look at this.

i've not personally used it yet, but it has been recommended a couple times in threads in the bass forum about building bass cabs.