Evolution Gun Works Cone Compensator Blank .708 575 x 40 Carbon Steel. However they do require a little work on your part. Gunsmith the Compensator Blank onto your host weapon and then install the barrel and compensator of your choice. Due to the thin barrels and short recoil these Compensators require some fine-tuning to achieve a proper tune. With that said they do offer a little extra work in the tuning process. Also the special thread pitches may require some re-threading of your barrel. Since there is no bushing they do require some re-threading of your barrel after the Compensator Blank has been installed. Specifications for Evolution Gun Works Compensator Blank: Manufacturer: Evolution Gun Works Color: Silver Fabric/Material: Steel Package Contents: Evolution Gun Works Compensator Blank Evolution Gun Works 11874: Cone Compensator Blank .708 575 x 40 Carbon Steel