This Luth-ARs .223/5.56 extractor O ring is designed specifically for use with .223 caliber and 5.56 caliber ARs and is made from durable, high-quality materials. The Extractor O Ring is designed to go over the bolt extractor spring, typically on short barreled applications to help with extractor reliability, ensuring that your AR operates smoothly and reliably. Luth-ARs .223/5.56 extractor O ring is easy to install and is compatible with .223 caliber and 5.56 caliber ARs.