rate contract for supply and installation of smf vrla batteries with fire flame retardant casing wherever indicated under buy back policy for various cns units in airports authority of india chennai airport for a period of 1 year rate contract for supply and installation of smf vrla batteries with fire flame retardant casing for 1 year , cat ( a ) -items to be supplied and installed. , supply & installation ofsmf-vrla batteries with fr casing as per annexure-vii, s.no-2 of nit document , cat ( b ) - buy back items , buy-back ( ie minus ) amount of old batteries ( as is where condition ) as per annexure-vii, s. no. 2 of nit document.