Dykes Ring, is a type of piston ring that has an "L" shaped cross-section with the back side of the "L" facing the cylinder wall. The purpose of this unique design is that the top part of the "L" is not sealed to the piston and is able to be acted upon by the hot gases produced during combustion. The force of these gases pushes the the ring against the cylinder wall to create a superior seal. The lower part of the "L" seals against the piston. This is often used on the top ring of the piston and placed at or near the crown of the piston due to its resistance to ring flutter.