PERSPEX® extruded acrylic is different from cast acrylic in terms of production process and molecular structure. Extruded acrylic sheets are produced by pushing the acrylic mass through a form, while the chemical process takes place. Extruded acrylic is therefore heterogeneous and its properties may vary depending on the direction of extrusion. 
The main advantage over the cast acrylic is better thickness tolerance and lower price.
Extruded sheets are UV resistant and have a 10 year guarantee.