Two swinger couples fucking together

Two swinger couples swap wives. It's not easy to understand for everyone but these two couples enjoy watching their partner enjoy themselves with other people and at the same time enjoy themselves too. One man fucks the wife of the other man who sucks the husband's dick. The other woman masturbates the girl who is being fucked and then the two women get into a doggy position to be fucked at the same time, watching as their partner fucks someone else while they do the same