The production of ten large are a Resistive Plate Chambers (RPCs) for the end-cap region of CMS, under India-CMS-RPC Collaboration—‘‘Action Plan(Phase-I)’’, is in progress at the Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai, inactive collaboration with Delhi University and Panjab University. These detectors are being assembled with gas-gaps fabricated in KODEL-Korea, mechanics from China and the FEBs from Italy. After testing and validating the series for REi/2,3, these chambers would be sent to CMS at CERN. This paper reports various pre-assembly jobs, leak tests and leakage current measurements of the gas-gaps, mechanical assembly and progress often RPC sunder production.