So factor twelve, factor eleven, factor ten and factor nine. So heparin acts as an anticoagulant by stimulating the binding of antithronbin three to thrombin and the other serum proteases, these ones that we mentioned just a moment ago. Now what do we mean by anticoagulant? Well, the process of coagulation means to form the blood clot. So anticoagulation means to not form the blood clots and that's exactly what the heparin does. It stimulates antithrobin three to basically inhibit the activity of throbin which means we cannot form those blood clots.