MKS Instruments, Inc. (MKSI) Ownership Summary provides a snapshot of institutional holdings and activity for a particular stock. The institutional holdings summary data encompasses the holdings and change from most recent 13F filings. The insider filer data counts the number of monthly positions over 3 month and 12 month time spans. Summary data is calculated daily, using the most up to date information available. Please Note: An FPI is exempt of filing insider holdings with the SEC. Therefore, it is recommended to visit the companyï¿½s website for up to date information.