Berkshire Partners, an investment firm based in Boston, has teamed up with the management at Implus Corporation to acquire a majority stake in the U.S. company, which owns a gaggle of accessory brands in the footwear and fitness markets. The stake was bought from Trilantic North America at an undisclosed price. Led by its chief executive, Seth Richards, and Todd Vore, president, Implus has rapidly expanded its offering in the last years through a spate of acquisitions. The brands owned by Implus include Sof Sole, Yaktrax, Airplus, Sneaker Balls, Little Hotties, Icetrekkers and many others. They cover product categories such as insoles, shoe care products, sports socks and fitness products. Earlier this year, Berkshire Partners agreed to buy The Rockport Company from the Adidas Group, together with other investors including New Balance Holding.