How to Determine if Reese Goose Box Fits Forest River RV Flagstaff Classic 371RK

Updated 12/15/2025 | Published 11/20/2024

Question:

Will this fit the Forest River RV Flagstaff Classic 371RK

asked by: Stanley F

Expert Reply:

Hi Stanley,

While I don't have a way to know for sure if the Reese Goose Box 5th-Wheel-to-Gooseneck Air Ride Coupler Adapter # RP85FR will fit your Forest River RV Flagstaff Classic 371RK, I can tell you how to determine it.

There are a couple of ways to do this, the first being to find the model number on a sticker or a plate somewhere on the pin box itself. However, if that sticker or plate is not there, the other way to find out what pin box you have is by taking a few measurements. I have added a link below to a help article called "4 Steps to Choosing Your 5th Wheel Pin Box" and if you scroll down a bit in the article, it walks you through the measurements that are needed.

The # RP85FR will fit so long as you have a Lippert 1621, 1716, 0719, or Rhino pin box.

expert reply by: Kyle S

Chris R.

12/15/2025

Hey Stanley, were you able to find the model number or take those pin box measurements on your Flagstaff Classic 371RK? Knowing that would show whether the Reese Goose Box fits. Your update could make it easier for others checking their setup too.