Men's Jammers (Swim Trunks)

Jammers end an inch or two above the kneecap and grip the leg the whole way there. Compression is the point: the fabric holds the thigh instead of resting on it, so nothing shifts or fills with water as you turn. Pockets, liners and loose hems appear nowhere on one, because each of them would cost you speed.

Fit and finish both come from racing. The leg is held by a rubberized band or a bonded hem, which stops the fabric riding up your thigh at the wall. Seams are often bonded or welded rather than sewn, since a stitched ridge along the inner thigh turns sore over 2,000 yards. Polyester blended with PBT, a chlorine resistant stretch fiber, is the usual build. It keeps its shape through daily training instead of sagging by the second month.

Swim briefs race the same events with less cloth and marginally less drag. What a jammer buys you is thigh coverage, so no rub where the legs meet and no burn on the back of the thigh in a shallow outdoor pool. Trunks and board shorts are not really rivals, since both fill with water and slow you to a stop. Cycling shorts look similar and are not interchangeable, because a jammer has no seat pad and no cushioning anywhere.

Squad swimmers, school teams and triathletes wear these by default, and adult lap swimmers who feel exposed in a brief land here too. Compression suits anyone whose thighs rub, since the fabric removes skin on skin contact for the length of the swim. A casual beach day is the wrong setting, where the fit reads as equipment and there is nowhere to put a key. Sunbathing suffers too, because the tan line lands mid thigh and stays all season.

Pull a new pair on dry and expect a fight, since a jammer that slides on easily is already too big. Look along the inner thigh seam and favor a bonded join you can barely feel over a stitched one. The waistband tie should be a flat drawcord you can knot, not a thin string that vanishes into the channel. A fresh water soak straight after training does more for the fabric than anything else. Shade drying protects both the color and the stretch.