Exhaust Coupling Straps
Products are available at:

DavesMotors.com

TeamGoNads.com

LargeScaleRC.com

and many other fine stores

These special ends lay flatter than any other zip tie or coupling strap. 

The curved base gives a better seal on the coupling.

This low profile makes for a cleaner look and reduced pinching of couplings.
They are 11" long and can strap up to 3" in diameter.
3/16"wide with a 50lb tensile strength. UV resistant black.

Perfect for almost all sizes of Nitro and Gas RC's!