By Modern Sink Lab. Research checked September 29, 2026. Document-based guidance; not a hands-on product test.
Affiliate disclosure: As an Amazon Associate I earn from qualifying purchases.
A thick countertop does not, by itself, mean you need an extended garbage disposal flange. The relevant thickness is the sink material where the drain flange and mounting assembly clamp together. If the approved standard assembly already fits the actual sink and disposer correctly, buying a deeper flange adds no useful upgrade.
For the InSinkErator mounting system covered by manual 79841-ISE Rev B, the extended-flange requirement starts above a ¾-inch sink thickness at the drain seat. The FLG-SSLG accessory is listed for ¾–1¾-inch material; confirm the exact combination at the ¾-inch boundary. That range does not establish compatibility with another manufacturer’s mounting system. The threshold table below separates flange length from the shorter-screw requirement.
If your actual problem is a high wall drain or limited cabinet space, compare compact disposal outlet heights and clearance before buying a flange. An extended flange addresses a thick drain seat; it does not raise a disposal’s waste outlet or solve an unrelated leak.
Measure the sink at the drain seat
The countertop supports or surrounds the sink near its rim. The disposal flange passes through the opening in the bottom of the bowl. Those are different locations, often made from different materials and with very different thicknesses.
Start with the exact sink drawing and the exact disposer installation manual. Look for the drain-opening section or the manufacturer’s stated mounting limit. If that dimension is absent, ask the sink maker or installer to establish the thickness at the actual drain seat. A thick apron front, a chunky-looking rim or a “fireclay” label is not a substitute for that measurement.
On an existing installation, do not dismantle a working disposer merely to obtain a shopping measurement. A plumber can assess the assembled mount, identify the current flange and decide whether removal is necessary. Keep the electrical and removal procedure with the installer and the product manual; this is a parts-selection guide.
Record three separate facts: the opening’s diameter, the sink thickness through which the flange passes, and the disposer’s mounting system. A nominal 3½-inch opening answers only the first question. The lip must seat properly, the prescribed mounting parts must fit beneath the sink, and the locking connection must match.
Shorter mounting screws and a longer flange solve different problems
The reviewed InSinkErator installation manual, 79841-ISE Rev B, identifies H1 as 1½-inch mounting screws and H2 as 1⅛-inch screws. Its steps 5 and 11 call for H2 when the sink is thicker than ⅜ inch; step 11 separately calls for FLG-SSLG when the sink is thicker than ¾ inch. These are instructions for the models covered by that manual, not a rule for every brand or older disposer.
On a narrow screen, swipe the table sideways to read every column.
| Measured condition | What the reviewed documents say | Buying implication |
|---|---|---|
| More than ⅜ inch, but below ¾ inch | Use the specified shorter H2 mounting screws under this manual. | Thickness alone has not crossed this manual’s extended-flange threshold. Check the complete approved mount. |
| Exactly ¾ inch | The accessory page describes a ¾–1¾-inch range; the installation manual says an extended flange is required above ¾ inch. | Confirm the exact sink/disposer combination at this boundary. Do not round a measurement to force a result. |
| Above ¾ inch through 1¾ inches | The manual requires FLG-SSLG above ¾ inch; the accessory is specified for sinks up to 1¾ inches thick. | Consider the genuine extended flange after the installer verifies seating and the mounting system. |
| Above 1¾ inches, or unknown thickness | The reviewed FLG-SSLG information does not establish suitability. | Stop the parts order and obtain a manufacturer-approved solution. |
A shorter screw can avoid a mounting interference described in the manual. It cannot turn a flange with insufficient usable depth into a longer one. Likewise, fitting a deeper flange does not authorize substituting arbitrary screws, omitting a retaining ring, stacking extra seals or forcing a mount together.
Three scenarios that lead to different purchases
A stone countertop with a thin stainless sink
Imagine a thick stone counter around an ordinary stainless bowl. The flange clamps at the bowl drain, so the stone thickness is not the flange decision. If the sink/disposer instructions approve the supplied assembly, keep it. Countertop thickness still matters for other fittings, including the soap dispenser’s mounting shank.
A replacement sink with a one-inch drain seat
One inch is an illustrative measurement, not a general fireclay specification. In the reviewed InSinkErator system it lies above the extended-flange threshold and inside the accessory’s stated range. That makes FLG-SSLG a candidate, conditional on the exact opening and mount. Obtain the sink and disposer model numbers before choosing a visually similar lower-priced flange.
A disposer outlet that conflicts with the wall drain
This is a separate vertical-layout issue. A flange advertised as “deep” is intended for thicker sink material; it is not a promise to recover cabinet or plumbing clearance. Have the installer check the final assembly with our sink depth and garbage disposal clearance worksheet. Changing a flange is not evidence that the drain route will work.
When the InSinkErator FLG-SSLG is worth considering
Consider it: your exact InSinkErator-compatible assembly calls for an extended flange, the measured drain seat is within the approved range, and the installer has confirmed the remaining mount and plumbing arrangement. The documented part is FLG-SSLG, catalog number 10082, in polished stainless steel.
Skip or pause: the supplied flange already meets the instructions; you only want to match a different finish; your disposer uses an unverified mounting system; or the problem is a damaged seal, poor seating or insufficient space below the bowl. Diagnose the cause before replacing parts.
The Amazon option below is the specific FLG-SSLG accessory, not a complete disposer or a complete mounting kit. Verify the current seller, package contents and return terms. A photo of a similar ring or a “universal 3½-inch” title does not establish this model match.
Check InSinkErator FLG-SSLG offers
The information to confirm before ordering
- Sink: full model and measured or manufacturer-confirmed thickness at the drain seat.
- Disposer: full model, current installation manual and identified mounting system.
- Part: approved flange SKU, finish and which associated mounting pieces are included or reused under the instructions.
- Final assembly: seating, retaining hardware, cabinet access and outlet-to-drain geometry confirmed by the installer.
If you are choosing a farmhouse sink, complete the cabinet and apron fit review separately. A successful flange match cannot establish that the sink itself fits the cabinet.
Research scope: InSinkErator US extended-flange product information, 2026 accessory catalog and installation manual 79841-ISE Rev B, including pages 2, 5 and 7; exact US FLG-SSLG listing. Related Amazon parts categories were reviewed before selecting the model. Rankings and retail availability are snapshots, not compatibility or quality guarantees. We have not physically fitted this combination.