Coaching or drilling alone falls apart when you spend half the hour picking up balls. This teaching cart carries up to 150 tennis balls in a removable Oxford cloth bag with a 12 by 12 by 13 in interior, deep enough that a feeding session runs from start to finish without a break. Breathable mesh panels let you see how many balls are left, and two zippers open the bag wide when it is time to reload.The frame is lightweight aluminum tube arranged in an X-shaped structure, a combination that resists rust through outdoor sessions on damp courts and holds its shape under a 66 lb load. Four universal wheels let the cart track along the baseline as a drill moves, and two of them lock so it stays put while you step away to demonstrate a stroke. Two side pockets take a phone, keys or a spare grip, which saves a second bag sitting on the bench.Portability is the other half of the story. The whole cart measures 16 by 16 by 36 in and weighs 7 lbs, so it lifts into a car trunk single-handed, and it folds down into a 37.5 by 6 by 6 in carry bag for storage in a hall cupboard or a club store room. Tennis coaches are the obvious users, but the same cart works for badminton shuttles, baseball, softball and pickleball practice, which makes it a sensible buy for a school, a club or a parent running backyard sessions.