The Quad Lock 360 Flat Rectangle 4-Hole Base is one of those accessories that exists to solve a problem most people don’t realize they have until they start building a custom mount. It is a flat, rectangular plate with a 4-hole drilling pattern and the company’s 360-series connector on top, designed to serve as the foundation for a phone mount in places where the standard handlebar or stem mounts don’t fit. It is not a standalone product in any meaningful sense — you need a 360-series arm, a phone case or adapter, and usually some hardware to attach it to something. Judged on that basis, it does its job, though with a few caveats worth understanding before buying.
The core of the product is straightforward. The plate is machined from aluminum, with a flat rectangular footprint and four countersunk holes arranged in a rectangular pattern. The top face carries the 360-series female connector, which accepts the company’s arms and extension pieces and locks them at indexed intervals. That indexing is the main functional advantage over a generic ball-and-socket plate: once you set an angle, it stays set, and you can rotate the phone between portrait and landscape without the mount loosening over time. The 4-hole pattern is the other selling point, since it lets you bolt the base to a flat surface with machine screws rather than relying on a clamp or strap.
In practice, this base is used in a few recurring scenarios. The most common is mounting a phone on a motorcycle, scooter, or bicycle in a spot where a handlebar clamp won’t work — on a fairing panel, a dashboard, a top triple clamp, or a custom bracket. It also shows up in cars, where people bolt it to a dashboard panel or a seat rail, and in boats, UTVs, and workshop setups. The flat plate and four holes make it easy to fabricate a simple adapter plate or attach it to an existing panel with a drill and a few bolts. That flexibility is the reason the product exists, and it works well when the installer has the tools and the patience to plan the mounting location.
Build quality is consistent with the rest of the 360 line. The aluminum body feels solid, the countersinks are clean, and the connector engagement is tight without being difficult to operate. The finish has held up in reports of long-term use, though like any anodized part it will show scuffs if it’s mounted in a high-wear area. The plate is small enough that it doesn’t add meaningful bulk, but the flat design means it needs a genuinely flat mating surface; mounting it to a curved or irregular panel will require a shim or a custom bracket, which undercuts the simplicity of the product.
The main limitation is that this is a part, not a solution. Buyers sometimes pick it up expecting a complete mount and then discover they still need an arm, a case, and hardware. The four-hole pattern is also not a universal standard — it matches the company’s own ecosystem and common aftermarket hole spacings, but it is not guaranteed to line up with every panel or bracket you might want to use. Drilling into a vehicle panel is permanent, and getting the placement wrong is an expensive mistake. Compared with a clamp-style mount or a suction-cup mount, this base trades convenience for security and a low profile; it is harder to install and harder to move, but far less likely to shift or be removed by someone walking past.
There is also the question of vibration. The base itself is rigid, and rigidity is good for holding an angle, but it transmits vibration directly into the mount. On a motorcycle, that means the phone’s camera stabilization and the mount’s joints do the damping work, and the base does none. Riders with expensive phones should factor in a vibration damper, which adds cost and bulk. This is not a flaw specific to this plate, but it is a trade-off that comes with any rigid, bolt-on mounting solution.
Who is this for? People who have a specific flat surface in mind and are comfortable drilling, bolting, or fabricating a small bracket. It suits motorcyclists building a custom dash setup, car owners who want a fixed mount in an unusual location, and anyone who values a low-profile, theft-resistant installation over something they can move between vehicles. It is also a reasonable choice for workshop or marine use where a clamp won’t grip.
Who is it not for? Anyone who wants a mount they can install in five minutes without tools, anyone unwilling to drill into a panel, and anyone who needs a complete out-of-the-box solution. If you ride a bike with a standard round handlebar and just want a phone in front of you, a handlebar clamp mount is simpler and cheaper. If you want to move the mount between cars, a suction or vent mount makes more sense. The 360 Flat Rectangle 4-Hole Base is a well-made component for a specific job, and it is worth buying when that job is actually yours.