For your 2021 Forest River travel trailer's roller shades with a 1" outside diameter (OD) tube, the correct replacement spring is typically the 0.75" (3/4") version. Although the tube measures 1" OD, the spring itself must be slightly smaller to fit inside properly. There are three standard spring sizes available: 0.75", 1", and 1.25". Since the 1" spring was too large, the 0.75" spring is the recommended choice and is commonly used for Valu-Line and similar RV roller shades. If you need assistance selecting the proper spring length or have additional details such as brand or model, further support is available. This ensures a correct fit and smooth operation of your RV roller shades.