IPO GMP comparison: Four public issues - BLS Polymers IPO, SFC Environmental Technologies IPO, M.K. Sons Fine Jewels IPO and Bombay Coated & Special Steels IPO are open for subscription on Thursday, 29 October.BLS Polymers IPO and SFC Environmental Technologies IPO opened for bidding on 27 October and will close today, 29 October.The grey market premium (GMP) of four ongoing IPOs — BLS Polymers, SFC Environmental Technologies, M.K.