Every question, answered.

Rocking is the whole reason for the shape. The wide flexible base spreads across the cushion or the deck instead of balancing on a point, and the fins keep the drink from rattling loose. A wake rolls through, the base flexes with it, and the drink settles back level.

No — nothing clamps to anything. That's deliberate: rail holders only work if you've matched the exact 1-1/8 or 1-1/4 inch profile, and they only serve whoever's sitting at the fence. This sits on top of whatever surface is closest and travels with the drink instead.

Measure the bottom, not the rim. A base 2 to 3 inches across fits — the 40 oz Stanley does, and so does a can in a hard insulated cooler. Handled travel mugs don't; the handle gets in the way of the fins.

Yes — a rocking boat isn't a stress test for this, it's the reason the base is shaped the way it is. It resists tipping and settles back after a wake hits. A direct hard knock still wins, same as it would against anything — but the ordinary sway of crossing someone else's wake is the everyday case this is built around.

Both, and the sun pad, the pedestal table, and the deck floor too. The base doesn't care what's underneath — it flexes to whatever surface it's on and grips the drink the same way each place it lands.

Understandable — marine vinyl sheds water, which means it sheds grip the moment a can starts sweating. The fins hold the drink by its bottom inch regardless of how slick the cushion underneath has gotten.

No adhesive, no clamps, nothing cut into the vinyl. It just sits on the surface, so there's nothing to tear or reupholster later — unlike a cut-in holder, it leaves the boat exactly as it found it.

Rinse it with the hose or run it through the dishwasher. It's one piece of flexible material with nothing to come apart, so lake water and sunscreen don't have anywhere to hide.

It's called the Steadi, molded in small runs in Orange, California by Steadi Labs — veteran-founded and patent pending. Every order ships free from steadilabs.com, with 30 days to change your mind.

Yes — it's one piece of flexible molded material with no hinge, adhesive, or metal hardware, so there's nothing for a season of sun and spray to corrode or work loose the way it does in a rail clamp's hardware or a swing holder's pivot. Rinse it with the hose along with the rest of the boat between trips.

Most crews do fine with two or three moving around the deck — one that lives near the cooler lid, since that surface gets used and cleared the most, and one or two more that travel with whoever's on the sun pad or the rear lounge, where the factory holders never reached. Since nothing clamps or mounts, moving one from the pedestal table to the tube-towing spotters takes a second, not a tool. A boat that regularly rafts up with others, or runs closer to its full fifteen-person rating, is the case for keeping a fourth aboard.

A practical one — new owners tend to discover the cup holder shortage themselves within the first few outings, right around the time they start looking at velcro strips like everyone else in the owners' groups. This solves it out of the box, with nothing to install and no rail size to check first.

It sits steady. A slim 12 oz seltzer can — the White Claw-style format — runs about 2.26 inches at the base, inside the 2 to 3 inch range the fins are built to grip, so it doesn't have the play it does rattling loose in a ring molded for a full-width standard can.

Yes — the fins grip whatever's actually set down, can or cooler, so a hard insulated sleeve that stands proud of a factory ring isn't a fit problem here. It only becomes one on a cooler bulky enough to push past the fins' 3.15-inch flex ceiling, which the common single-can Colster-style sleeves don't.

Not one that actually works for everything people search it for. Owner threads hunting for an expander or adapter for the factory rings run into the same wall: a ring molded at one fixed diameter can't flex to also fit a hard insulated cooler and a 40 oz tumbler, because those containers span a wider range than a rigid ring was ever built to cover. A base with fins that grip the bottom inch, instead of a ring with one fixed bore, is the actual answer to what people are searching for.

Rail holders only ever serve the one seat next to the fence, and a pontoon's whole point is a deck that seats far more people than that. This isn't a replacement for what's mounted at the helm — it covers the sun pad, the pedestal table, the rear lounge, and the cooler lid, the surfaces a rail clamp physically can't reach because they're nowhere near a rail.

Yes — that's exactly the gap it's built for. The rear lounge is where spotters ride while the driver tows a tube, and factory cup holders don't reach back there. This doesn't mount to anything, so it sits on the cushion the same way it would on the sun pad or the pedestal table, and the fins hold the drink through the turns that come with towing.