This is symmetrically spaced bat tattoo. Right foot bats has no fill only outlines and left foot has full filled black bats. Bat tattoo has many meanings and one of them is that bat is a symbol of communication because they're highly social creatures.
Those magnificent and matching Best Friend Tattoo Designs can speak volume; it has and it will always be a great symbol of friendship and bond. Best friend tattoo designs do not necessarily have to be conceptual.