The 6001 lightweight overshirt size guide:

1. **Underarm Vents for Breathability:**
The 6001 Lightweight Overshirt is designed with underarm vents to provide enhanced breathability and ventilation. This feature ensures you stay comfortable and cool even in warmer weather or when engaged in more active pursuits.

2. **Shorter Sleeve Ending at the Wrist, Vintage Worker Style:**
The overshirt features shorter sleeves that end at the wrist, reminiscent of vintage worker-style shirts. This design element adds a classic and timeless touch to the garment. When trying on the overshirt, ensure that the sleeves hit just at your wrists or slightly above, allowing for ease of movement without the sleeves bunching up.

3. **Functional, Tapered Cuff Featuring a Popper Button:**
The 6001 overshirt comes with functional and tapered cuffs, featuring a popper button closure. This design allows you to secure the cuffs comfortably and adds to the practicality of the overshirt. Make sure the popper button fastens securely to keep the cuffs in place while wearing it.

4. **Torso Fit Same as #3001 or #3002, with Less Tapered Hem:**
The torso fit of the 6001 Lightweight Overshirt is similar to the #3001 or #3002 overshirts. It offers a relaxed and comfortable fit through the chest and waist, making it suitable for layering over base layers. However, the hem is less tapered compared to the mentioned overshirts, providing a more relaxed and casual appearance.

5. **Nickel-Free Popper Fastening:**
The 6001 Overshirt is equipped with nickel-free popper fastenings. These buttons are durable and eco-friendly, contributing to the overall quality and sustainability of the garment.

When selecting your size for the 6001 Lightweight Overshirt, consider the following:
- Refer to the brand's size chart and measurements to find your ideal fit based on your chest and waist measurements.
- Take into account your preferred fit. If you like a roomier and relaxed style, opt for your regular size. If you prefer a more tailored look, you may consider sizing down, but ensure it still offers enough room for layering and movement.
- Check the sleeve length and cuffs, ensuring they fit comfortably around your wrists and provide ease of movement.

As with any clothing item, personal preferences may differ, so trying on the 6001 Lightweight Overshirt in different sizes can help you find the one that best suits your style and comfort. The overshirt's combination of vintage-inspired design and functional features makes it a versatile and trendy addition to your wardrobe. Enjoy the lightweight and stylish appeal of the 6001 Overshirt!