Opened public offering of 8 million common units representing limited partner interests. Monthlong option for underwriters to purchase up to 1,200,000 additional units was granted by Summit Midstream Partners Holdings. Net proceeds will fund part of purchase price for a pending acquisition of Red Rock Gathering Co. LLC’s membership interests. No proceeds from units sold by Summit Midstream Partners Holdings will be received. Barclays, BofA Merrill Lynch, Morgan Stanley, Deutsche Bank Securities Inc., RBC Capital Markets, Citigroup Inc., Goldman, Sachs & Co. and Wells Fargo Securities LLC were book-running managers.