Black & Decker Electric String Trimmer Spool Line Replace Rewind

BLACK & DECKER 6 Amp 14 in. Trimmer Edger Model GH710 string rewind. Refill Spool. Automatic Feeder. I believe Home Depot sells a 3 pack for around $20. Update Sept 2018: I bought a new spool and read the official directions. They say wind the both the top and bottom in the same direction of the arrows. I did that and sometimes it would auto feed but most times it would not. The plastic on my spool is physically damaged from lots of use which could be the cause of the problem. Whenever I needed to feed more line I loosened the spool and fed it by hand.