01 What makes it unique
The 3901RK is built for living aboard. A U-shaped raised kitchen commands the rear wall, a mid-coach living room with a 50-inch Smart TV and a convenient half bath sits just inside the door, and a sliding barn door opens to a front master suite with a king bed, dual-sink full bath, a 48-by-30 shower and a walk-in wardrobe with washer/dryer prep. Five slides open the interior to near-residential proportions, and the front basement storage is oversized with slam-latch baggage doors.
It is a heavy, long coach. RVUSA lists a 42-foot-4 length and five slides; the published dry weight is 14,755 pounds against an 18,000-pound GVWR and a 3,245-pound payload — figures that are internally consistent (dry plus payload equals the rating). One source (Camping World) lists a lighter 16,800-pound GVWR and a 42-foot-2 length; the factory-consistent 18,000-pound figures are used here and the discrepancy is noted. An 18-cubic-foot residential refrigerator, a 24-inch range, a JBL three-zone stereo and a La-Z-Boy hide-a-bed in its own slide round out the interior.
At an MSRP of $133,778 it is the full-timer’s rear-kitchen plan in the luxury line — a coach for a couple who cooks seriously and lives aboard, and one that needs a one-ton truck, often a dually, to tow safely loaded.
02 Full specifications
Dimensions
- Exterior length
- 42' 4"
- Exterior width
- 8' 0"
- Exterior height
- 13' 5"
- Interior height
- 7' 0"
Weights
- Dry / unit base weight
- 14,755 lbs
- GVWR (max loaded)
- 18,000 lbs
- Net cargo / payload
- 3,245 lbs
- Dry pin weight
- Not published*
Capacities
- Fresh water
- 70 gal
- Grey water
- 88 gal
- Black water
- 88 gal
- Refrigerator
- 18 cu ft
Construction
- Frame
- 12" I-beam · z-frame
- Walls
- 2" laminated fiberglass · lauan
- Roof
- Alpha TPO · walkable, 5" rafters
- Underbelly
- Four-Season · heated, 0° tested
Running gear
- Axles
- 2 (tandem)
- Hitch
- Fifth-wheel (in-bed)
- Suspension
- MORryde® CRE3000 · wet bolts
- Cooling
- Coleman Mach 15K · 50A
Galley & bath
- Cooktop
- 3-burner recessed
- Refrigerator
- 18 cu ft
- A/C
- 15K Coleman Mach heat-pump (triple-15K opt)
- Water heater
- Quick-recovery · gas/electric
Sleeping & layout
- Sleeps
- 4
- Slides
- 5
- Hitch type
- Fifth-wheel (in-bed)
- Primary bed
- King
03 The Montana floorplan family
Montana is Keystone's flagship luxury fifth wheel and the best-selling luxury fifth wheel in North America. The line runs to fifteen floorplans for 2026; the six highest-demand layouts are profiled here in full, and the rest — along with the lighter, lower-profile Montana High Country sub-line — are catalogued on the line hub. The 3901RK on this page is highlighted; each other profiled plan links to its own page.
| Floorplan | Nominal | Sleeps | Notable |
|---|---|---|---|
| 3123RL | 35 ft | 4 | Rear-living entry, kitchen island |
| 3100RL | 36 ft | 4 | New-2026 widebody, rear-living couples |
| 3231CK | 37 ft | 4 | Rear living, kitchen island + dual pantries |
| 3531RE | 39 ft | 4 | Rear entertainment, glass-door pantry |
| 3532SP | 39 ft | 4 | Side patio, king bed, theater seating |
| 3795FK | 40 ft | 6 | Front raised kitchen, rear full bath, sleeps 6 |
| 3623EB | 40 ft | 4 | Rear living, bike garage, four slides |
| 3761FL | 41 ft | 6 | Front living, bath-and-a-half, 5 slides |
| 3781RL | 41 ft | 4 | Best-selling rear living, kitchen island |
| 3857BR | 41 ft | 8 | Middle bunkroom + loft, family |
| 3901RK | 42 ft | 4 | Rear kitchen, bath-and-a-half, front master |
| 3915TB | 43 ft | 6 | Two full baths, bunkroom + loft |
| 3941FO | 43 ft | 6 | Front office full-timer, outside kitchen |
Montana is the best-selling luxury fifth wheel in North America and Keystone's flagship towable. The full line runs to fifteen floorplans for 2026, plus the lighter, lower-profile Montana High Country sub-line catalogued separately on the hub. Body specifications (lengths, heights, payload, tanks, refrigerator, sleeping, slides and A/C) are RVUSA-verified against the 2026 structured spec records, each page fp-slug and title checked; pin (hitch) weights are from the same records. Montana publishes a 18,000-pound GVWR across the luxury line; the lighter three-slide 3123RL entry carries a derived 16,580-pound GVWR, and the new widebody 3100RL has its dry weight and GVWR flagged as derived. Real loaded pin weights run higher — always weigh the loaded coach and confirm against your truck's payload and rear-axle ratings.
04 What owners & reviewers report
Rear U-shaped kitchen
A wraparound raised galley on the back wall — the serious cook’s layout, with a half bath off the mid-coach living room.
Front master suite
A private front bedroom with a king bed, dual-sink full bath, 48-by-30 shower and a walk-in wardrobe with washer/dryer prep — a bath-and-a-half full-timer plan.
Five slides, full-timer size
A 42-foot-4 coach on five slides — near-residential interior volume for living aboard, needing a one-ton truck to tow loaded.
Source conflict noted
The factory-consistent 18,000-lb GVWR (dry 14,755 + payload 3,245) is used; one source lists a lighter 16,800-lb GVWR and 42-ft-2 length — weigh the loaded coach and confirm the door sticker.
05 How it compares
The best-selling rear-living plan — a shorter, lighter four-slide coach without the rear kitchen or front master suite.
The front-office full-timer plan — trades the rear kitchen for a workspace and an outside kitchen at a similar size.
Grand Design’s full-timer flagship fifth wheel — the natural luxury cross-shop for living aboard.