01 What makes it unique
The 3915TB is the biggest Montana profiled here and the one that solves the single hardest problem in a shared fifth wheel: bathrooms. It is one of the few fifth wheels on the market with two full bathrooms — not a bath-and-a-half, but two complete baths — with the second served by its own dedicated second entry door. A middle bunkroom with a loft above it sits between the baths and the private rear bedroom, making it a true family-and-guests coach at 43 feet.
Its capacities are scaled to match. The 3915TB carries a 137-gallon grey tank and a 98-gallon black tank — by far the largest holding tanks of the profiled plans, sized for the second bathroom and extended stays — on the standard luxury build of a 12-inch z-frame chassis, walkable Alpha TPO roof, Four-Season package and La-Z-Boy furniture, with a king bed, a 50-inch living-room TV and a single 15,000-BTU Coleman Mach heat-pump air conditioner standard. RVUSA and multiple dealer records agree on a 15,222-pound dry weight and the line’s 18,000-pound GVWR, with a 2,780-pound dry pin and a 2,778-pound payload.
At an MSRP of $137,228 it is among the most expensive plans in the luxury line, and at 43 feet with two baths it is firmly full-size fifth-wheel territory needing a properly rated heavy-duty truck. For a large family, or anyone who routinely travels with guests and refuses to share one bathroom, the two-full-bath 3915TB is the flagship of the profiled Montana lineup.
02 Full specifications
Dimensions
- Exterior length
- 43' 0"
- Exterior width
- 8' 0"
- Exterior height
- 13' 4"
- Interior height
- 7' 0"
Weights
- Dry / unit base weight
- 15,222 lbs
- GVWR (max loaded)
- 18,000 lbs
- Net cargo / payload
- 2,778 lbs
- Dry pin weight
- 2,780 lbs
Capacities
- Fresh water
- 70 gal
- Grey water
- 137 gal
- Black water
- 98 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
- 6
- Slides
- 4
- 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 3915TB 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
Two full bathrooms
Not a bath-and-a-half — two complete baths, the second with its own entry door — a rare and sought-after fifth-wheel feature.
Largest holding tanks
137-gallon grey and 98-gallon black — by far the biggest tanks of the profiled plans, sized for the second bath and long stays.
Family-and-guests flagship
A 43-foot middle-bunkroom-and-loft plan between two baths and a private rear suite — the most accommodating profiled layout.
Full-size truck required
At 43 feet and the line’s 18,000-lb GVWR, this is heavy-duty-truck territory — confirm payload and rear axle on a 3/4- or 1-ton.
05 How it compares
The lighter family plan — the same bunkroom-and-loft idea with one bathroom, shorter and a touch more payload.
The full-timer alternative — trades the second bath for a front office and an outside kitchen at a similar size.
Grand Design’s flagship fifth wheel — the natural luxury cross-shop against the largest Montana plans.