Riverlake Partners sold SemiTorr Group Inc. to fellow private equity firm Transom Capital Group LLC for an undisclosed sum.

Tualatin, Ore.-based SemiTorr, which has eight distribution centers across the U.S., provides high purity gas and fluid handling systems and components to the microelectronics, sanitary and industrial markets. Riverside bought a controlling stake in SemiTorr in 2012.

Transom invests in middle-market companies, while Riverlake makes leveraged control growth investments in small, profitable businesses.

O'Melveny and Myers LLP and Perkins Coie were the M&A and debt finance advisers, respectively, to Transom. Bank of America Merrill Lynch and PNC Mezzanine Capital provided debt financing for the deal.