The Adtran Slack Storage Unit (vendor part 1187772G1, Millennium part 653989) mounts to the rear of an Adtran TA350 ONT outdoor housing and adds room for up to 50 ft of extra drop cable slack at the network interface. It gives installers a way to store service loop without coiling excess fiber loosely at the enclosure, protecting bend radius outside the elements. FTTH installation crews use it on drops that run longer than the ONT housing alone can store. Millennium stocks the matching TA350 ONT housing and other Adtran outside plant accessories.