Keystone Montana 3900RK vs Forest River Riverstone 39RKFB

Keystone · Fifth Wheel

Keystone Montana 3900RK

—

Forest River · Fifth Wheel

Forest River Riverstone 39RKFB

~$155,215

The difference that matters

These two luxury rear-kitchen fifth wheels run past 42 ft, and the Montana 3900RK is the bigger one in nearly every direction. It weighs 17,085 lb dry with a 3,405 lb pin, sleeps six and holds 77 gal fresh, 150 gray and 100 black. Its Four Season Living Package adds a heated, enclosed underbelly and dump valves, and it has ABS brakes, Lippert Titan leveling and fireplaces in the bedroom and living room.

The Riverstone 39RKFB is 16,121 lb with a 2,950 lb pin and a higher cargo allowance of 2,829 lb against 2,320. It pairs a rear kitchen island with a front bedroom across four slides, rides on 8,000 lb axles and has heated holding tanks and a heated docking station, though no four-season rating. It sleeps four.

The Montana's extra 50 gal of gray capacity matters most on long stays without a sewer connection.

Keystone Montana 3900RK: Full-timers who stay put in cold places and want the largest gray tank and room for six
Forest River Riverstone 39RKFB: Heavy-duty truck owners, traveling as a couple, who want a slightly lighter pin and more cargo allowance.

Weights

2027 maker figures

Dry weight (UVW): 17,085 lb
GVWR: not published
Pin weight, dry: 3,405 lb
Cargo capacity (CCC): 2,320 lb

Weights

2027 maker figures

Dry weight (UVW): 16,121 lb
GVWR: 18,950 lb
Pin weight, dry: 2,950 lb
Cargo capacity (CCC): 2,829 lb

2,829 lb between brochure dry weight and GVWR. Water (8.3 lb a gallon), food, gear, propane and dealer-added options all come out of it.

Spec for spec

	Keystone Montana 3900RK	Forest River Riverstone 39RKFB
Dry weight (UVW)	17,085 lb	16,121 lb
GVWR	—	18,950 lb
Hitch / pin weight, dry	3,405 lb	2,950 lb
Cargo capacity (CCC / OCCC)	2,320 lb	2,829 lb
GVWR minus dry weight	—	2,829 lb
Exterior length	43.8 ft	42.67 ft
Exterior height	13.3 ft	13.42 ft
Sleeps	6	4
Slide-outs	—	4
Fresh water	77 gal	79 gal
Gray water	150 gal	100 gal
Black water	100 gal	100 gal
Factory solar	None	—
House battery	—	Two dual 6V/12V slide-out battery trays (batteries not specified)
Generator	—	LP generator prep

Bold is the lighter or larger figure. A dash means the maker does not publish it.

To scale

051015202530354045 ft

Keystone Montana 3900RK · 43.8 ft long · 13′4″ tall
Forest River Riverstone 39RKFB · 42.67 ft long · 13′5″ tall

Drawn to one scale from each camper's listed length and, where the maker publishes it, its exterior height. Outlines are typical for the camper type, not traced from this model. The figure is a 6 ft person. The dashed blue line is 25 ft, the length about 93% of national park campgrounds accept.

Keystone Montana 3900RK

Full spec sheet, sources →

Forest River Riverstone 39RKFB

Full spec sheet, sources →