Zero International 321AA 36" Sill Protection Automatic Door Bottom with Neoprene Insert - Surface Mounted - Clear Anodized Aluminum

Up to 1 inch of effective drop is what the 321AA gives you, and the seal compresses against the floor rather than just resting on it, so it will close out an uneven slab or a worn saddle within that range. The neoprene insert drops from the housing in a scissor motion when the door closes and lifts back up when it opens. If your gap under the door exceeds 1 inch at any point along the sweep path, this one will not reach it.

Yes, handing has to be specified on the 321AA. The plunger that triggers the seal sits at one end of the housing and has to land against the frame on the hinge side, so a left hand unit will not work on a right hand opening. Get the handing of the door before you place the order.

The 321AA carries a Fire Rated-UL10c performance rating, so it can go on a fire rated opening. That matters because a lot of surface sweeps and door shoes are smoke or weather products only and will fail an inspection on a labeled door. Confirm the drop clearance your label requires, then mount the housing to the door face.

The 321AA is supplied in a 36 inch length, which suits a standard 36 inch wide door leaf. Zero automatic door bottoms are cut to size in the field from the non-plunger end when the door is narrower. If your door is wider than 36 inches, order the longer length rather than trying to make this one work.

Surface mounted, like the 321AA, means the aluminum housing screws to the face of the door at the bottom, so you can retrofit an existing door with no routing and no removing the door from its hinges. A mortised automatic door bottom is let into a channel cut in the bottom rail and sits nearly hidden, which is what you want when appearance matters or the door is already prepped for one. For a door already hung and in service, surface mounted is the far less invasive job.

It is rated for 5 million cycles and built as a commercial product, but it is a regular duty unit. On a heavily used entrance, a stairwell door on a busy floor, or an exterior door taking abuse, look at a heavy duty automatic door bottom instead. For office, corridor, and dwelling unit doors in a multi-family or institutional building, regular duty is the right class.

The 321AA ships with #321 end caps included. You will still need to plan for the mounting fasteners into the door face and, on a metal door, the right screws for that substrate. Install instructions for Zero automatic door bottoms are published by the manufacturer and worth pulling before you drill, since the plunger projection has to be set against the frame.

A brush or blade sweep drags on the floor every time the door swings, which wears the seal, scratches finished flooring, and adds drag to the closer. The 321AA lifts its neoprene seal clear of the floor whenever the door is open and drops it only when the door closes, sealing on the hinge side first so it never hangs up mid swing. On carpet, thresholds, or any opening where a dragging sweep would bind, that is the whole reason to use one.

Clear anodized aluminum is the standard mill finish on aluminum storefront and it reads as the same silver tone as most aluminum frames, thresholds, and door shoes. The 321AA housing is aluminum in a clear anodized finish, so on an aluminum entrance it disappears into the assembly. Against dark bronze or painted hollow metal it will stand out.

Neoprene is the insert on the 321AA and it takes weather, ozone, and temperature swings better than a plain vinyl blade, which is why it is the common choice on exterior and smoke rated openings. It stays flexible in cold and compresses tight against an uneven floor rather than deforming permanently.