I use the Boss Buck gravity feeders. They make them in 300# 600# and the 1200#. Their web site is www.bossbuck.com. I have been very happy with them, no bird problem and feed stays dry, and they are reasonably priced.
They hold up very well, I have had some for 4 years now, I use them for bucks, does and fawns. For the fawns I made shorter legs for them.
We use Outback feeders and they are great! They will last forever and we like that they don't have a lot of supports around the feeding tubes - less for bucks to hook or damage their antlers on. Also, they can add a fawn tube feeder that comes down right in the middle. Their website is www.outbackfeeders.com The owners are great people and hard workers. You can see their feeders occasionally on our TV show, Wild Rivers Whitetails, on the Pursuit channel. We highly recommend them.