For the deepest soak, pick the Kohler Underscore K-1130 (17-1/8-inch water depth, 81 gallons). For an easier step-in, pick the Kohler Archer K-1123 (60 × 32) or K-1946 (60 × 30), both with a 19-inch step-over. Confirm the cutout, floor load and hot-water supply before the deck is built, and buy the drain separately.
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This guide compares three acrylic drop-in bathtubs and the details that decide whether they fit your deck and your water heater.
Drop-in tubs compared (Kohler spec sheets)
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| Bath | Size / cutout | Water depth / capacity | Weight / min. floor load |
|---|---|---|---|
| Underscore K-1130 | 60 × 32 × 21 in. / 58-1/2 × 30-1/2 in. | 17-1/8 in. / 81 gal | 75 lb / 58 lb/ft² |
| Archer K-1123 | 60 × 32 in. / 58-1/2 × 30-1/2 in. | 15 in. / 58 gal | 70 lb / 44 lb/ft² |
| Archer K-1946 | 60 × 30 in. / 58-1/2 × 28-1/2 in. | 15-1/8 in. / 57 gal | 58 lb / 45 lb/ft² |
A drop-in tub has a finished rim that rests on top of a deck or platform. The tub body hangs through a cutout, and the deck is finished with tile, stone or another surface. Unlike an alcove tub, it has no finished apron or wall flange, so the deck design is part of the job. The deck is where the size and cutout figures above matter most.
Kohler Underscore K-1130: the deep soaker
Choose the Kohler Underscore if a deep soak is the point. The K-1130 spec sheet (resources.kohler.com) lists a 60 × 32 × 21-inch acrylic bath with integral lumbar support, a slotted overflow that allows deep soaking, a 17-1/8-inch water depth and an 81-gallon water capacity. It can be installed drop-in or undermount; the sheet notes a kit is required for undermount installations, sold separately.
That depth has a cost. It weighs 75 pounds empty and lists the highest minimum floor load of the three at 58 pounds per square foot. Kohler also says the hot water supply should be 70 percent of the bath’s capacity or more; for 81 gallons, that is about 57 gallons of hot water, so check what your water heater can deliver. Our water heater size calculator can help.
On October 15, 2026, the standard new offer from eFaucets showed stock with model 1130-0, White.
Check Kohler Underscore K-1130-0 60 x 32 drop-in bath (white) on Amazon →
Kohler Archer K-1123: 60 × 32 with a lower step-over
Choose the Kohler Archer K-1123 for a standard 60 × 32-inch drop-in that is easier to step into. The K-1123 spec sheet (resources.kohler.com) lists Kohler’s Comfort Depth design, which it says gives a 19-inch step-over height while keeping the depth of a standard 21-inch bath, plus integral lumbar support, a slotted overflow and a textured bottom surface.
Kohler lists a 15-inch water depth, 58-gallon capacity, 70 pounds empty and a 44-pound-per-square-foot minimum floor load. Its cutout is the same 58-1/2 × 30-1/2 inches as the Underscore, so the two share a deck opening size; check each tub’s full drawing before you assume anything else matches.
On October 15, 2026, the standard new offer from eFaucets showed limited stock with model 1123-0, White.
Check Kohler Archer K-1123-0 60 x 32 drop-in bath (white) on Amazon →
Kohler Archer K-1946: for a narrower 30-inch space
Choose the Kohler Archer K-1946 when your deck is 30 inches deep, not 32. The K-1946 spec sheet (resources.kohler.com) lists a 60 × 30-inch acrylic bath with the same Comfort Depth 19-inch step-over, lumbar support, slotted overflow and textured bottom as the K-1123.
It lists a 15-1/8-inch water depth, 57-gallon capacity, 58 pounds empty, a 45-pound-per-square-foot minimum floor load and a 58-1/2 × 28-1/2-inch cutout. It is the lightest of the three.
On October 15, 2026, the standard new offer from eFaucets showed limited stock with model 1946-0, White.
Check Kohler Archer K-1946-0 60 x 30 drop-in bath (white) on Amazon →
Before you order: deck, cutout and access
Get the maker’s cutout dimension before the deck is framed and topped, and confirm it against the exact model you are buying. Kohler’s sheets also say to measure the actual product for rough-in details, because dimensions are nominal.
Plan an access panel to the drain and overflow. A drop-in deck closes in the waste and overflow, so you need a way to reach them later. Our access panel guide covers sizing.
Check the floor. Kohler lists a minimum floor load on each sheet, from 44 to 58 pounds per square foot for these tubs. A filled deep tub with a person in it is heavy; if you are unsure about your framing, have it checked before installing.
The drain and overflow are sold separately
All three sheets list a required drain: Kohler K-7271 brass or K-7272 PVC slotted overflow bath drain, sold separately. The slotted overflow is what gives these tubs their listed water depth, so use a drain made for it.
Each tub has a reversible drain, meaning it can be installed with the drain at either end; decide which end before the deck and plumbing are built. Our bathtub drain types guide explains drain styles, and our overflow gasket guide covers the overflow seal.
Choosing the faucet
Drop-in tubs usually take a deck-mounted faucet on the platform or a wall-mounted faucet above it. The K-1130 drawing shows no faucet holes in the tub itself, so the faucet is planned with the deck; check the drawing for the exact model you buy.
Check spout reach so water lands inside the rim. Our Roman tub faucet guide covers deck-mount fillers and our wall-mount tub faucet guide covers wall-mount options.
Plan the valve and the hot water supply together. Kohler’s rule of thumb, hot water at 70 percent of the bath’s capacity or more, means the water heater is part of the decision for a deep soaker.
Drop-in vs alcove vs freestanding
Pick a drop-in when you want a tiled or stone deck around the tub, or when the tub sits in a corner or under a window. Pick an alcove tub for a standard three-wall opening with a shower; our alcove bathtub guide compares those. Pick a freestanding tub when you want it on the open floor with no deck; our freestanding tub guide covers those.
Frequently asked questions
What is a drop-in tub?
A tub with a finished rim that rests on a deck or platform. The body sits through a cutout and the deck is finished around it.
What size cutout does a drop-in tub need?
It depends on the model. Kohler lists 58-1/2 × 30-1/2 inches for the Underscore K-1130 and Archer K-1123, and 58-1/2 × 28-1/2 inches for the Archer K-1946.
Does a drop-in tub come with a drain?
Not these. Kohler lists a required K-7271 or K-7272 slotted overflow bath drain, sold separately.
How much hot water does a deep drop-in tub need?
Kohler says the hot water supply should be 70 percent of the bath’s capacity or more. For the 81-gallon Underscore, that is about 57 gallons.
Which Kohler drop-in tub is easiest to step into?
The Archer K-1123 and K-1946 list Kohler’s Comfort Depth design with a 19-inch step-over height.
How we chose
This document-based guide makes no hands-on testing claim. We read Kohler’s spec sheets for the Underscore K-1130, Archer K-1123 and Archer K-1946 and inspected the K-1130 drawing. On October 15, 2026, all three linked standard new offers showed stock or limited stock from eFaucets. American Standard Evolution tubs were checked but excluded because current maker records were not found. Read our selection method and about Plumbing Picks.
Primary sources
- Kohler Underscore K-1130 spec sheet (resources.kohler.com): 60x32x21, acrylic, drop-in or undermount, 81 gal, 17-1/8 in., 75 lb, 58 lb/ft², cutout, required drain, 70% hot water note.
- Kohler Archer K-1123 spec sheet (resources.kohler.com): Comfort Depth 19 in. step-over, 58 gal, 15 in., 70 lb, 44 lb/ft², cutout.
- Kohler Archer K-1946 spec sheet (resources.kohler.com): 60×30, Comfort Depth, 57 gal, 15-1/8 in., 58 lb, 45 lb/ft², cutout.