Let's check out hedge fund activity in other stocks similar to MKS Instruments, Inc. (NASDAQ:MKSI). We will take a look at LPL Financial Holdings Inc (NASDAQ: LPLA ), REGAL-BELOIT CORPORATION (NYSE: RBC ), Avista Corp (NYSE: AVA ), and The Medicines Company (NASDAQ: MDCO ). All of these stocks' market caps resemble MKSI's market cap.