The Phase 5 LPSN was developed as an improvement to their previous quad rail. The new LPSN was inspired by lots of beneficial features that shooters have requested and demanded from them and other manufacturers. The slender design, longer nose, ease of installation and superior construction are some of the features that they designed into this system. Another development feature is the finish quality. The LPSN undergoes a rigorous extra de-burring process in order to ensure a smoother snag free finish. The details and level of care during the manufacturing of the LPSN make it the perfect choice for your Carbine or Pistol build. Unfortunately their Pigtail gas tube will not fit correctly under the LPSN (Lo-Pro Slope Nose Quad Rail)