There are three kinds of knee pads on the market that cover most of the trades. Hard-shell, gel, and hybrid. The differences matter and the right answer is trade-dependent.
Hard-shell pads — exterior is rigid plastic, interior is foam or gel padding. The hard plastic shell lets you slide on the surface (concrete, plywood, drywall scraps) without dragging your knee. Sliding is a real benefit for tile setters, concrete finishers, anyone who shifts position constantly without standing up.
Gel pads — softer outer fabric, gel-based padding inside. Stay where you put them, don't slide. Better impact absorption than hard-shell because the gel deforms more than plastic does. Best for stationary kneeling work — flooring install in fixed positions, electrical inside a panel, anyone who kneels and stays kneeled for long periods.
Hybrid pads — gel core inside a hard outer shell. Best of both worlds in theory. In practice, slightly heavier and more expensive, sometimes the gel-and-shell interface creates a hot spot. The good ones are excellent. The cheap ones are worse than either pure design.
Strap design is half the battle. Knee pads with a single strap behind the knee slide down within an hour. Two-strap designs — one above the knee, one below — stay put. Slip-on (no strap, held by a sleeve over the knee) work for short tasks but lose grip after a few hours of movement. For all-day work, two-strap is the only option that works.
Some pants have built-in knee pad pockets — the Carhartt double-knee with the EVA insert pocket, for example. Those work fine for occasional kneeling but the foam inserts are thin and don't compare to a real strap-on pad for heavy use. If you're a tile guy, get the real thing.
Replace knee pads when the cushioning compresses to less than half its original thickness. Press the pad with your thumb. If it doesn't bounce back, retire it.
We stock most of the major brands and a couple of trade-specific ones. Tile setters tend to leave with hard-shell. Flooring installers tend to leave with gel. Roofers — depends on the slope.