Jumbo Thistle Sack White. These socks look great in any backyard with Goldfinches on them. They also attract many other birds including Pine Siskins, Redpolls, Purple Finches, and other birds. The draw string at the top helps to make sure that if your nyjer sock is knocked down in a storm or high winds you don’t loose that precious nyjer seed like other feeders. The nyjer sock is made of nylon ensuring you a long life and a full yard of birds for many years to come.