Each single longitudial strip has a core of high modulus,low creep polyester yarn bundles encased in the tough,durable polyethylene sheath which give a grid like shape to the composite.The geogrid has superior unidirectional strength and is available as a customer-made product in a range of strengths between 100kn/m up to 1000kn/m.Bidirectional strength can be obtained by installing two geogrid layers at right angles