Samson Evolution 4in. Extension Black. We carry thousands of top brand-name products like the Samson Evolution 4" Extension Tactical Rails all with incredibly low prices. We back everything we sell with dedicated customer support and the professional expertise of in-house product experts who can help you find exactly what you need - not to mention free shipping options. You want it and we've got it - so pick up a Samson Evolution Series 4" Rail Extension today The Evolution 4" Extension allows users to extend their EX series rail past the piston block or front sight base. Can also be used to add length to standard Evolution rails. Specifications for Samson Evolution 4in Extension: Manufacturer: Samson Color: Black Finish: MIL-A-8625 type III class 2 anodizing Fabric/Material: 6061-T6 Aluminum Weight: 4.4 oz Condition: New Package Contents: Samson Evolution 4" Extension Samson 01-03013-01: Evolution 4in. Extension Black