18mm Matrix Percolator Shisha Filter 45 DegreeThis 18mm 18mm Shisha Filter features a matrix percolator. The Shisha Filter features a 18mm female connector on top and a 45 degree angle 18mm male connector to attach to your waterpipe. The matrix percolator is a cylinder that is located at the centre of the waterpipe base. It often has both vertical and horizontal slits, giving you the super high volumes of vapour diffusion. It helps the waterpipe produce a much smoother hit.