It is made of two horseshoe-shaped islets , Manuae to the west and Te Au O Tu to the east , with a total area of 6.17 kmÂ on either side of a lagoon about 7 km x 4 km . It comprises two horseshoe-shaped islets , Manuae to the west and Te Au O Tu to the east , with a total area of 6.17 kmÂ on either side of a lagoon about 7 km x 4 km .