Equistone Partners, a private equity firm, completed the acquisition of a majority stake in SF Filter, a distributor of mobile and industrial filters, from Ambienta, an asset manager. Financial terms were not disclosed. “We felt it was vital to find a reliable partner who not only offers the necessary financial capacity but can support us in our future growth by bringing years of experience in helping scale companies. We have found just such a partner in Equistone," Daniel Infanger, SF Filter CEO.