The "Frog Jump in Water sound room acoustics tweak" looks particularly interesting!!
Yes, notice in the description for that one:
"The Frog Jump in Water Sound Tweak comprises 4 small plastic containers 12x6x8 plus Detailed Instructions how to implement the tweak.
The value of this product is primarily in the instructions - the 4 plastic containers, while suitable for the purpose, are quite inexpensive."
I'm sure if I get it, I will hear details in the recording I never noticed before. "What I thought were just 'drumsticks' I am now quite sure are Vic Firth American Heritage AH5A's made of maple with a 9% moisture content." Sweet.
Steve