How can you keep squirrels out of bird feeders?

there is a bird feeder that is built so that it will hold the weight of the bird but not anything heavier. any other animal will cause the wholes where there is access to food to close. i'm not sure the name of the brand but our Walmart carries it. i think specialty pet stores do to.How can you keep squirrels out of bird feeders?
simple is ask someone who selling bird feeders, then if they has something to keep away from bird feeder by spin around when squirrels sit on themHow can you keep squirrels out of bird feeders?
Put up a squirrel guard so that they can't get to the bird feeder.
We attached a frisbee to the top of our bird feeder and left it loose enough so that it spins.When squirrels try to get on it from the top they spin around and fall off.Also,make sure that it's high off the ground and not too close to branches

bumble and bumble