FIN COMB RING by Supco FCR6 The FCR6 Supco Handy Ring fin comb tool is used to straighten damaged fins on evaporator and condensing units. This tool repairs bent fins so your unit will run with top efficiency. The Supco Model #FCR6 fin straightening tool has 6 fin combs with two fin comb sizes on each comb. This tools gives you 12 fin comb sizes to fit almost all air conditioning coils with fins that range from 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, & 20 fins per inch.