The Echo 1 Ver. 2 Spring Guide is sturdily constructed from S303 Stainless Steel for the version 2 gearbox. And, this spring guide features bearings that prevents the spring from building unnecessary tension by twisting and distorting in its seat. This spring guide is OEM by Modify and imported under the Echo 1 name. Echo 1 series of upgrade parts are compatible with most major brands of AEG. You can expect the same level of quality from these parts as Guarder and Systema parts for a fraction of the price.