Standard Power Rifle Length Buffer Spring.The Green spring is for use in A1 / A2 fixed stock rifle length receiver extensions (buffer tubes) with rifle length buffers. It is also extremely popular in intermediate depth (7.75 “ deep) VLTOR A5 buffer tubes with 4” A5 buffers. The spring design loads of the Green spring are those of a BRAND NEW mil-spec buffer spring. While the Green spring is primarily for use with lesser calibers such as .223, 5.56. 6.8 SPC, 6.5 Grendel, 7.62 X 39, etc. in A2 rifle length tubes, it may sometimes be appropriate for use in long BBL (20”+) rifle length gas BBL’s in heavier calibers such as .308 and 6.5 CM, .260 Rem, etc.. (May not be effective for unsuppressed 7.62 X 51) In the latter scenario, an H2 or H3 carbine buffer has been used successfully in rifle length tubes with the Green spring. Over gassed heavier caliber guns with rifle length tubes may be addressed with our Red or Orange carbine springs and standard length 3.25” carbine buffers along with a spacer to yield the appropriate tube depth for the longer BCG’s. Color Coded GREEN