Boston-based Mack Investors LLC has bought 23 Rainin Road in Woburn for approximately $4.8 million.

The 56,290-square-foot office/flex facility is situated on 12.1 acres and serves as a primary office and research facility for Rainin Instrument, developer, manufacturer and distributor of pipetting products and services.

Boston-based commercial real estate firm Grubb & Ellis Co. represented the Rainin Group and the estate of Kenneth Rainin, prior owner of the facility. Financing was secured through Digital Federal Credit Union of Marlborough.

The Rainin Group will continue conducting its operations in the facility under the terms of the company’s lease, which runs through 2011.