The AFL Fiber Containment Vault Extension (vendor part FCV-EXT-2-1, Millennium part 528491) adds 8 in of depth to a 24 in x 36 in AFL switchblade vault, letting crews adjust grade height on buried fiber installations without swapping the whole vault body. Molded HDPE construction resists ground moisture and soil stress over the life of the install. Placing and construction crews use extensions like this to match vault height to finish grade on handhole and manhole builds. Millennium stocks the matching switchblade vault bodies and covers for the same product line.