rigsize

Forest River Sierra 399LOFT mattress size

Years 2020–2025Sold as Sierra DestinationLength 40' 8"
Bunks44 × 74 in Bunk. Forest River spec sheet, 2023. Common RV bunk sizes →

Bunk mattresses in 44 × 74 in

Some bunks have a rounded corner, so trace yours before a custom cut. A thicker bunk mattress takes headroom from the bunk above.

Custom size
Mattress Insider Luxury Gel Memory Foam

Mattress InsiderLuxury Gel Memory Foam

  • Memory foam
  • 8 in thick
  • not stated
Made to 44 × 74 inGet a quote

Bed sizes by year

YearMain bedBunksOther bedsSource
2020–44 × 74 in–Forest River spec sheet
2023–44 × 74 in–Forest River spec sheet

Years not listed weren't published.

The 399LOFT floorplan

Forest River Sierra 399LOFT floorplan, 2023

Forest River's 2023 399LOFT floorplan.

Is this your 399LOFT?

Check the year and length against your RV before you order.

YearModelLengthSleeps
2020Sierra Destination 399LOFT40' 11"–
2023Sierra Destination 399LOFT40' 8"–
2024Sierra Destination 399LOFT40' 8"–
2025Sierra Destination 399LOFT40' 8"–

Other Sierra mattress sizes

40DUPLEX403RD420FLAll Sierra floorplans

Sources

  1. Forest River (forestriverinc.com), archived copy: https://web.archive.org/web/20190922205734/https://forestriverinc.com/rvs/destination-trailers/sierra-destination/399LOFT/4170
  2. Forest River (forestriverinc.com), archived copy: https://web.archive.org/web/20190915135034/https://forestriverinc.com/ImageHandler.ashx?ImageID=90054
  3. Forest River (forestriverinc.com), archived copy: https://web.archive.org/web/20221206170515/https://forestriverinc.com/rvs/destination-trailers/sierra-destination/399LOFT/6450
  4. Forest River (forestriverinc.com), archived copy: https://web.archive.org/web/20221206174729/https://forestriverinc.com/ImageHandler.ashx?ImageID=221103
  5. Forest River (forestriverinc.com), archived copy: https://web.archive.org/web/20250116045611/https://forestriverinc.com/rvs/sierra-destination/399LOFT/8257
  6. Forest River (forestriverinc.com), archived copy: https://web.archive.org/web/20260114144801/https://forestriverinc.com/rvs/sierra-destination/399LOFT/10032

Questions

What size are the Forest River Sierra 399LOFT bunk mattresses?

44 × 74 in (Forest River spec sheet, 2023).