- Hybrid
- 13.25 in thick
- Soft / Medium / Firm
Sleep Foundation: Best Mattress Overall Read review
That's an RV king, 6 in narrower than a regular king (76 × 80 in). A regular king won't fit, so get an RV king in exactly 70 × 80 in.
About the RV king size →Keystone spec page, 2027.
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Sleep Foundation: Best Mattress Overall Read review
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Some bunks have a rounded corner, so trace yours before a custom cut. A thicker bunk mattress takes headroom from the bunk above.
Sleep Foundation: Best Mattress for Pressure Relief Read review

The Sprinter bedroom. Measure the platform, not the old mattress, before you buy.
| Year | Main bed | Bunks | Other beds | Source |
|---|---|---|---|---|
| 2024 | – | 36 × 74 in | – | Keystone spec sheet |
| 2026 | 70 × 80 in King | – | – | Keystone 2026 brochure |
| 2027 | 70 × 80 in King | – | – | Keystone spec page |
Years not listed weren't published.

Keystone's 2027 3900DBL floorplan.
Check the year and length against your RV before you order.
| Year | Model | Length | Sleeps |
|---|---|---|---|
| 2023 | Sprinter Limited 3900DBL | 43 ft 6 in | 10 |
| 2024 | Sprinter Limited 3900DBL | 43 ft 6 in | 10 |
| 2025 | Sprinter 3900DBL | 43 ft 6 in | 10 |
| 2026 | Sprinter 3900DBL | 43 ft 6 in | 10 |
| 2027 | Sprinter 3900DBL | 43 ft 6 in | 10 |
The main bed is 70 × 80 in (Keystone spec page, 2027).
36 × 74 in (Keystone spec sheet, 2024).