The largest cuticle protein family, the CPR family, contain a 35 amino acid R&R consensus (named after Rebers and Riddiford, PMID:2462055), which in an extended form has been shown to bind chitin (PMID:15475300). (Adapted from FBrf0242484.)
FBrf0200175 states that CG15756 and CG15515 came up in the initial survey for cuticular proteins with the R&R Consensus, but 'did not appear to code for cuticular proteins'. They are included in the CPR gene group as they contain the characteristic domain as defined by the Matrisome project (FBrf0242747).