The ERGO Never Quit Magwell Grip reconfigures the squared shape of the AR/M4 magazine well. – Reconfigures the squared shape of the AR/M4 magazine well into an ergonomic and comfortable grip option – Gives AR/M4 receivers a distinctive aesthetic upgrade – Easy installation – Oil and solvent resistant Santoprene® construction – NTOA Recommended – This fits AR-15/M-16 lower receivers with a removable trigger guard. It does not fit AR-10 large frame receivers or receivers with a permanently attached trigger guard.