Kevin Mulligan has brought the distinction between thick and thin descriptions into the philosophy of relations, and with its help he has put forward the theses that all relations are "thin" and internal, and that none is "thick" and external. Accepting and using Mulligan's thin–thick distinction, I argue that not all internal relations are thin. There are thick internal relations, too; and they abound in mathematical physics. Also, I claim that there might be thin external relations. However, introducing a distinction between strongly and weakly internal relations, I agree with Mulligan that all strongly internal relations are thin relations.