The Challenger incorporates the successful design of the piston valve with double action for more power. 
Double Action Piston Specification:- 
Silver solder construction, Re-heating coil. 
Double acting piston valve. 
9.5 bore, 14.0 stroke. 
Displacement lubricator. 
Forward and reverse action by slip eccentric. 
Weight 2100g. 
Dimensions 178 × 137 × 270 mm. 
1 packet of Solid Fuel and 1 bottle of Lubrication Oil are included with each model ordered.