You could follow the pack to the newest superstore to buy the latest, lightest titanium racket, but they're not going to let you take a few home for a test drive. They're not going to cut a deal on the synthetic strings or the state-of-the-art sneakers. Heck, they won't even throw in a can of balls. Worse, they're not going to find the stick that's just right for your game. Because they don't know any better. "The mass merchants don't know their equipment," owner Kevin MacDonald says, standing near a rack of court apparel crammed into his closet-sized store. "You can only get the expertise you need at a specialty shop. And those shops are all but gone." MacDonald ought to know; tennis is in his blood. His grandfather was stringing rackets in the 1930s. His father Norman--a national champion in the 1940s, and dubbed Mr. Tennis of Minnesota in the 1950s--opened Twin City Tennis as a hobby. Now, almost 50 years later, Kevin's kids help with the business, which caters to amateurs, hard-core hackers, high school champs, and college teams from St. Thomas to the University of Minnesota. "They're fourth-generation stringers," he says of his two sons. Watching him light-up, you'd swear he'd just served an ace.