Slipcovers

I want to buy covers for my sofa and loveseat, and I was wondering if someone could tell me what they regard as the best material for them. What do you find to be the most sustainable? What hardware do I stay away from? Thank you

Mine are a mixture of cotton and poly .. they are real ... and when I clean them I just throw them into the washer
Here is the site I got mine from

http://www.surefit.net/

I also bought one for my sofa, faux suede microfiber can be washed in the machine. Very durable. You can try www.seventhavenue.com. They have some models that you can love.