The Cyma FMR (Full Metal Rack) piston is one of the strongest on the market. 
It features a full rack of steel teeth and a sturdy but slightly flexible body to better absorb shock. 

We use this piston in all of our AEG builds, it is more than capable of handling all levels of stress and is our go-to piston for virtually every build. 
 
These pistons may arrive with the piston head attached depending on the stock we can source. 
The piston heads are strong but not suitable for use with AoE correcting buffer pads and should be removed if one is being used. 

The piston heads are considered a free extra :)
 
Please note the colour of the piston body may differ from the photo