'X' "Lighters", known to the soldiers as 'Beetles', carried about 500 men, displaced 135 tons and were based on London barges being 105 feet, 6 inches long, 21 feet wide, and 7 feet, 6 inches deep. The engines mainly ran on heavy oil and ran at a speed of approximately 5 knots. The sides of the ships were bullet proof, and was designed with a ramp on the bow for disembarkation. A plan was devised to land British heavy tanks from pontoons in support of the Third Battle of Ypres, but this was abandoned.