Modern Sink Lab researches manufacturer documents and product listings; this is not a hands-on product test. As an Amazon Associate, we earn from qualifying purchases. Specifications and purchase destinations checked September 29, 2026.
For a complete kitchen sink basket strainer, check the bare drain opening, the sealing flange and the thickness of the sink at the drain. “Fits a 3½-inch sink drain” does not tell you that a replacement basket will fit your existing drain body, or that a complete assembly can clamp a thick fireclay sink.
Conditional choice: KRAUS ST-1 is a documented complete drain assembly for a non-disposal bowl with a specified 3½- or 4-inch opening. Check the sink maker’s compatibility and drain-seat thickness before ordering. If you only need a lost lift-out basket, identify the existing assembly instead of buying this entire drain. Check the KRAUS ST-1 complete drain assembly on Amazon.
First decide which part you are replacing
| What you need | What must match | Common wrong purchase |
|---|---|---|
| A removable basket or stopper | Existing drain-body model, basket diameter, stem and locking mechanism | A generic “3½-inch” basket that refers to the sink opening rather than the basket itself |
| A complete non-disposal drain assembly | Bare sink opening, flange seating area, drain-seat thickness and pipe connection | A drop-in mesh catcher or stopper without the threaded body and mounting parts |
| A garbage-disposal connection | Disposal-compatible flange, mount and sink thickness | A basket-strainer body stacked between the sink and disposal |
The distinction matters when shopping: the Kitchen Drains & Strainers bestseller list contains many inexpensive removable catchers. Those products can be useful, but they are not interchangeable with a drain assembly sealed and clamped to the sink.
Three dimensions to record before buying
1. The bare opening in the sink
Use the sink’s exact specification or a measurement of the exposed opening when the existing assembly is removed. Measuring across a removable basket or the visible flange can give the wrong number. Many kitchen sinks use a 3½-inch opening, but bar sinks and specialty designs can differ. A “standard” label is a reason to check, not a substitute for checking.
2. The top flange and its seating area
The flange must cover the opening and seal on the intended surface. It is naturally larger than the opening. Also check the area underneath: a locknut or retaining cup may need more room than the top flange suggests. A curved drain recess or nearby sink structure can interfere even when the opening diameter is correct.
3. Sink thickness at the clamping point
Measure the material where the assembly passes through the bowl, not the countertop, apron front or rim. The body must accommodate the manufacturer’s gasket, washer and tightening arrangement. Total assembly height is not maximum sink thickness. You cannot subtract a flange dimension from a product’s overall height and assume the remainder is usable clamping reach.
A concrete example: what ST-1 tells you, and what it does not
KRAUS lists ST-1 for 3½- or 4-inch drain openings. Its specification shows a 4½-inch top flange and 3¾-inch overall height, with a 1½-inch NPSM connection callout. The drawing also shows a wider lower span, so leave room to assemble and service the underside.
Those numbers explain why a 4½-inch visible flange is not evidence that your sink has a 4½-inch hole. They also do not establish a maximum fireclay thickness: the checked sheet does not state one. For a thick or unusually shaped drain seat, ask KRAUS and the sink manufacturer to confirm the exact pair before ordering. An unanswered thickness question remains a reason to hold the purchase.
Karran’s L-2 is another useful example of the naming problem: it is described for a 3½-inch opening, while its published overall footprint is about 4⅝ inches and its height is about 4 inches. That larger outer size is not a claim that it can clamp a thicker sink. We did not verify a purchase destination or a maximum clamping thickness for L-2, so it is a dimensional example here rather than an alternative buying recommendation.
When a basket strainer is the wrong solution
A disposal normally replaces the non-disposal drain assembly and mounts with its own approved flange system. KRAUS specifically says ST-1 is a strainer, not a connector for a disposal. On a double-bowl sink, one bowl can have a basket assembly while the other uses a disposal, but each drain needs its own compatible connection and the shared pipe route still needs checking.
If thickness is the problem on a disposal bowl, use our disposal-flange thickness guide. If you are checking the drain supplied with a KBU44 sink rather than buying a standalone replacement, use the KBU44 grid and drain-kit check first; you may already have the required assembly.
The short buying checklist
- Exact sink model and bare drain-opening diameter.
- Flat sealing area and local drain-seat thickness.
- Complete assembly versus basket-only replacement.
- Approved gasket and clamping arrangement for the sink material.
- Pipe connection and the space needed below the drain.
- Written confirmation for any thickness or shape not covered by the model instructions.
Record an unresolved fit question in the three-candidate sink and drain comparison sheet. Do not turn a retailer’s “universal” description into a confirmed pairing.
Sources and scope
Dimensions were checked against the KRAUS ST-1 specification sheet and its kitchen-strainer installation manual; the disposal distinction is also stated in KRAUS’s ST-1 FAQ. The Karran L-2 product specification is used only to explain dimension labels. We reviewed Amazon’s relevant U.S. bestseller categories first, then verified ST-1’s exact model and assembly listing. We did not perform a leak test or validate an unspecified sink-and-drain combination.
For a double-bowl layout, decide which bowl should receive the garbage disposal before assigning the two drain assemblies. Compare the food-prep routine and the actual space beneath each bowl.
After confirming dimensions, match the drain sealing method: supplied gasket, compatible putty or specified silicone. The exact assembly drawing and material instructions decide which method belongs at each joint.