How to regain your throttle response and horsepower. Along with fixing that annoying coffee can pipe sound. 
Same quality used in performance manufactured Exhaust packing.  for 8-13 inch long cans.  To fit 2 inch to  2-1/2 inch I.D.  Cans. 
Dense weave high temp fiber glass packing. 
Often used in 
Wicked 
Trinity 
Jolly Moto
JL 
Toomey 
CPI 
Scheer 
Pro circuit 
FMF
Pretty much every silencer option