Well, basically, it's the speed at which these molecules can actually move along that membrane. So the higher the speed, the greater the likelihood that the molecules will move away. And so the higher the recovery rate is. So it turns out that phospholipids in general can move at a rate of about 1 μm squared per second. So that basically means every single second, that phospholipid can move 1 μm along that membrane. So, once again, these phospholipids generally move with a uniform constant value at a rate of about 1 μm squared per second.