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New 2026 Grand Design Momentum M-Class 399M

The New 2026 Grand Design Momentum M-Class 399M is built for RVers who want top-tier luxury combined with serious toy hauling capability. Featuring a spacious 13-foot garage, this floorplan is perfect for bringing along motorcycles, ATVs, or side-by-sides while still offering a high-end residential interior. The garage easily converts into a flexible living and sleeping space with rollover sofas, a HappiJac bed system, and a loft above, giving you plenty of room for guests or family.

The main living area offers a wide-open layout with multiple slide-outs, creating a true residential feel with theater seating, a large sofa, and an entertainment center for relaxing after a day of adventure. The kitchen is designed for real cooking on the road, featuring a large kitchen island, residential refrigerator, cooktop, oven, microwave, and abundant cabinetry, while the bath and a half layout adds extra convenience, especially for guests using the garage area.

Toward the front, the private master suite provides a comfortable king bed, wardrobe storage, and dresser space, creating a quiet retreat at the end of the day. The main bathroom includes a spacious residential-style shower and vanity, while outside, dual power awnings and large exterior storage compartments create the perfect outdoor setup for relaxing and entertaining. With its versatile garage, luxury features, and Grand Design craftsmanship, the Momentum M-Class 399M is built for both adventure and comfort.

Key Features & Highlights

13' toy hauler garage for motorcycles, ATVs, or gear
• HappiJac bed lift system with convertible seating
• Loft sleeping area for additional guests
Bath and a half for added convenience
• Spacious living area with theater seating and sofa
Kitchen island for meal preparation and serving
• Residential refrigerator, cooktop, oven, and microwave
• Private front bedroom with king bed
• Large bathroom with residential-style shower
• Dual power awnings for outdoor living
• Exterior storage compartments for camping gear

Why Choose Campers Inn RV

When you choose Campers Inn RV, you’re partnering with a team dedicated to helping you enjoy the RV lifestyle with confidence. Our RV Match Makers work closely with you to find the perfect RV for your travel goals, lifestyle, and budget. Every new RV we offer is carefully inspected and prepared by certified technicians so it’s ready for adventure. With flexible financing options, transparent pricing, and dependable service support whenever you need it, Campers Inn RV of Knoxville makes RV ownership simple and exciting.

See It In Person Today

Experience the luxury, space, and adventure-ready design of the Grand Design Momentum M-Class 399M for yourself. Call or text 865-933-7213 today to schedule your walkthrough or learn more from the team at Campers Inn RV of Knoxville.

New 2026 Grand Design Momentum M-Class 399M

Type: Fifth Wheel
Condition: NEW
Year: 2026
Manufacturer: Grand Design
Brand: Momentum M-Class
Model: 399M
Weight (Dry/Gross): 19170 lbs / --
Sleeps: 4
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