Perturbers in the giant arc La Flaca. Scale and orientation are shown on the image. Color-coded circles mark multiple images of three background sources. La Flaca is extremely thin and one of the longest known arcs. It is located between the two main mass clumps in El Gordo. Small-mass perturbers create additional multiple images. These perturbers are marked with arrows. The approximate position of the critical curve can be estimated by extrapolating the ratio of distances between knots 2.1a–2.1e and knots 2.2a–2.2e. The point where one expects the critical curve is marked with the cyan circle having 1″ radius. The two cyan ellipses within this circle mark a possible double counterimage. If these two objects are counterimages of each other, the critical curve would be very close to the middle point between the two. The small cyan circle labeled A marks a possible caustic-crossing object.