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The key, and the wall it has to cross

Pet door tags, keys and tunnel extensions

Two accessories decide whether a pet door works in your house rather than in the photograph: the key your animal carries, and the tunnel that gets the door through your wall. Tags are brand-specific and cheap; tunnel extensions are brand-specific and not. We list both by fitment, with the wall thicknesses each extension covers and the brands that have quietly stopped making theirs.

By

What we recommend

  1. Sure Petcare RFID collar tag for microchip cat flaps

    Sure Petcare RFID collar tag

    An RFID tag for the collar, working with SureFlap microchip flaps and pet doors, SureFeed microchip feeders and Felaqua Connect — the fallback when a chip reads badly.

    Works with
    All SureFlap microchip cat flaps and pet doors, SureFeed microchip feeders, Felaqua Connect
    Function
    Selective access without relying on the implanted chip
    Amazon reference
    DE B00B5BEK54 · US B018F2HSFO · GB B018F2HSFO · FR B018F2HSFO · IT B018F2HSFO · ES B018F2HSFO
    EAN
    5060180390341
    • Solves the one failure mode of a microchip door — a chip that has migrated or reads intermittently
    • Works across the whole Sure Petcare range, including the feeders
    • It hangs on a collar, and collars come off — which is the problem chips were meant to solve

    Best for: A cat whose chip the door reads unreliably — and as a spare before that happens.

    Check price on Amazon
  2. SureFlap 50 mm tunnel extender for microchip cat flaps

    Sure Petcare Tunnel extender, 50 mm

    A 50-millimeter tunnel extension for SureFlap cat flaps, compatible with the standard, DualScan and Connect models.

    Adds
    50 mm (1.97 in) to the flap’s standard 70 mm (2.76 in) tunnel
    Compatible with
    SureFlap Microchip Cat Flap, DualScan, and Microchip Cat Flap Connect
    Amazon reference
    B0D9H9LYWS (identical on 6 markets)
    EAN
    5060180394370
    • Turns a flap designed for a door into one that fits a wall
    • Stackable: several extenders cross a thick wall
    • Proprietary — nothing else fits properly, and a badly sealed tunnel is a draft

    Best for: Fitting a SureFlap into anything thicker than a door panel.

    ≈ $21
    Check price on Amazon
  3. Manruta pair of blue round RFID microchip collar tags for pets

    Manruta MRT RFID collar tag, 2 pack

    Two waterproof epoxy RFID collar tags for SureFlap and SureFeed, at $5.50 each — with a stated serial-number cutoff and a stated incompatibility.

    Tags in the pack
    2
    Price per tag
    $5.50
    Diameter
    1.1 in
    Weight
    2.8 g (0.1 oz) each
    Material
    Waterproof epoxy
    Power
    None — passive RFID
    Stated compatibility
    SureFlap Microchip Pet Door, Cat Door, DualScan Cat Door, SureFeed feeder
    Serial threshold
    Cat Door serial numbers above 1152201
    Stated incompatibility
    PetSafe products
    Read range
    Not published
    Amazon reference
    B07T5D43RQ
    EAN
    0717877418370
    • Publishes a serial-number threshold, which can be checked on the door you already own
    • Writes down the brand it will not work with, in its own capitals
    • No read range published

    Best for: A SureFlap door whose cat has no readable chip, or a second animal to add

    Check price on Amazon
  4. SureFlap tunnel extender three pack in white

    SureFlap Tunnel extender, 3-pack

    A three-pack of 50 mm (1.97 in) tunnel extenders in white, for SureFlap microchip cat flaps, DualScan and Connect models — 150 mm (5.91 in) of wall in one purchase.

    Contents
    Three extenders, 50 mm (1.97 in) each
    Material
    White plastic
    Compatible with
    SureFlap Microchip Cat Flap, DualScan and Connect
    Amazon reference
    B0DX2LZQBX (identical on 6 markets)
    EAN
    5060180394387
    • Cheaper per extender than buying them singly
    • 150 mm (5.91 in) covers most cavity walls in one order
    • Still proprietary, and still an unexpected cost on top of the flap

    Best for: A wall installation, ordered at the same time as the flap rather than a week later.

    Check price on Amazon
  5. Cat Mate pack of two collar magnets for electromagnetic cat flaps

    Cat Mate 04170257 collar magnets, 2 pack

    Two collar magnets for Cat Mate electromagnetic flaps, at $7.00 each — the simplest key on this shelf and the least selective.

    Magnets in the pack
    2
    Price per magnet
    $7.00
    Technology
    Magnetic — not RFID
    Power
    None
    Weight
    27 g (1 oz) for the pair
    Stated compatibility
    Cat Mate electromagnetic cat flaps
    Selectivity
    None — any matching magnet opens the flap
    Magnet strength
    Not published
    Amazon reference
    B0002DHNJQ
    EAN
    0035368702570
    • Nothing to pair, nothing to charge and nothing to go out of date
    • No serial number threshold and no firmware generation to check
    • No selectivity — a neighbor’s cat wearing any matching magnet gets in

    Best for: A Cat Mate electromagnetic flap where simplicity matters more than selectivity

    Check price on Amazon
  6. PetSafe electronic pet door RFID collar key with battery

    PetSafe PAC19-15793 Electronic Pet Door Key

    A powered RFID key for PetSafe Electronic Pet Doors, battery included, stated to last three to six months and not to work with the SmartDoor Plus.

    Keys in the pack
    1
    Price per key
    $24.93
    Technology
    Powered RFID
    Battery
    RFA-67, included
    Battery life
    3 to 6 months, depending on use
    Stated compatibility
    All sizes of the PetSafe Electronic Pet Door
    Stated incompatibility
    SmartDoor Plus
    Pets per door
    Up to 5
    Collar fit
    Fits most collar ID tags
    Weight
    20 g (0.7 oz)
    Read range
    Not published
    Amazon reference
    B000WJ0IGU
    EAN
    729849110458
    • Names the one door in its own range that it will not open
    • Battery included, and the part number given — RFA-67 — so a replacement can be found
    • The most expensive key here at $24.93, and sold singly where the others come in pairs

    Best for: A PetSafe Electronic Pet Door, as a replacement key or a second animal

    Check price on Amazon

Finding your need in door tags & tunnels

Opening the flap without a chip

A tag lets an unchipped animal, or one whose chip is not read, use a selective cat flap.

Sure Petcare Tunnel extender, 50 mm

Not weighing on a cat's neck

A tag adds to the collar and sometimes to the tracker, on a four-kilo animal. The weight stated in grams adds to the rest, and it is the total that matters.

Sure Petcare Tunnel extender, 50 mm

The buyer behind each kind, in door tags & tunnels

Unchipped animal
The tag is then the only way to use a selective flap. It gets lost, unlike the chip.
Chip not recognized
Some chip types are not read by some flaps. The tag sidesteps the problem.
Protected passage
A tunnel extends the flap through a thick wall. Without it the door does not open properly within the depth.

The downsides that come with door tags & tunnels

Tag against chip
The chip never gets lost and is not read by every model; the tag works everywhere and falls off the collar.
A tag recognized by your own cat flap
Tags and tunnels are specific to the flap's brand. There is practically no generic equivalent.
Tunnel against insulation
A tunnel gets through a thick wall and creates an air passage. Double-flap models limit that drawback.

The questions people ask about door tags & tunnels

When is a tag needed?

When the animal is not chipped, or when its chip is not of a type the flap reads. Otherwise the chip is enough.

Does the tag get lost?

That is its main flaw: it falls off the collar, above all with a safety fastening. Keep a spare.

Is a tunnel needed?

In a thick wall, yes: without it the door does not open properly within the depth and the animal hesitates.

Are tags universal?

No, they are specific to the flap's brand. There is practically no generic equivalent.

How many tags can be stored?

It depends on the flap model, as with chips. The number is in the instructions.

Does the tunnel let air through?

A long tunnel creates an air passage. Double-flap models limit that drawback markedly.

Does a tag work alongside a chip?

Most flaps accept both in memory at once, which lets you mix the household's animals.

Does a tag work in the rain?

Passive resonant tags have no battery and take water without trouble. What defeats them is extreme cold on the rare battery models, not damp.

Worth remembering, on door tags & tunnels

The tag exists for animals that are not chipped or whose chip is not read: it works everywhere and gets lost, unlike the chip. Tags and tunnels are specific to the flap's brand — there is practically nothing generic.

Door tags & tunnels in brief

  • Weight: 2.8 to 27 g (1 oz) for the pair, on 3 of the 6 models.

Door tags & tunnels, side by side

There is no table here, and the reason is in the listings. The figure published most often across these 6 products is stated compatibility, given by 3 of them — short of the four in five a column needs to compare rather than to display gaps. Each product page says what its own maker published.

Sources, and how we decide

Specifications: manufacturer sheets for pet devices and the matching Amazon product pages. Prices and availability: Keepa.

Most recent revision in this category: October 6, 2026.

The way we judge door tags & tunnels

Prices quoted in these summaries are dated readings. The live price is shown next to each product.