Compact auxiliary basis sets matched to the standard aug-cc-pVnZ and aug-cc-pV(n + d)Z orbital basis sets have been developed for use as resolution-of-the-identity (RI) sets in explicitly correlated F12 calculations. The resulting RI errors from using these sets have been benchmarked in calculations of atomization energies and electron affinities for a number of representative small molecules. These errors were always more than an order of magnitude smaller than the residual basis set error for a given choice of orbital basis set. (C) 2009 Elsevier B.V. All rights reserved.