Gap size of a disk surrounding a binary/multiple stellar system vs. separation from the companion to the primary. The filled circles show the disks with gaps, and the filled diamonds are for the disks without gaps. The filled boxes connected by a solid line are for the source FL Cha of which two possible separations are given in Cieza et al. (2013). The open triangles show the disks with gaps but without known companions. The separations for these disks are the detection limits at given mass ratios of companions to primaries (see Appendix A). The left-pointing arrows are used to indicate that it could be still possible that there are companions at smaller distances than the detection limits. The dotted lines mark the 1:1 and 10:1 relation between gap sizes and separations. The dashed lines show the predicted relation between gap sizes and separations from Pichardo et al. (2008) with e = 0 and 1.