ENGPAR Sales Pvt. Ltd. Offers Flat Top Design Piston. ENGPAR Sales Pvt. Ltd. Supplies piston rings. Flat Top Design Piston is manufactured from high quality aluminum alloy as per International Standards. Flat Top Design Piston is available in the diameter ranging from 25mm to 225mm. These pistons are applicable for diesel engines, air compressors, automobiles, tractors, generators and refrigerators. These are also available in other designs which include dome top, reverse dome top, hollow dome top and other unique designs.