The J series is the older model, while the F series represents the updated version. The two series differ significantly in terms of functionality and design, with specific distinctions as follows:

1. **Saw Blade Tension Adjustment**
The J series saw blade requires manual tension adjustment, and there is no standardized tension setting.
In contrast, the F series saw blade features automatic tension adjustment and emits a prompt sound once it reaches the optimal tension level.

2. **Upper Wheel Cleanliness & Maintenance**
The J series is equipped with a fixed, embedded upper wheel, making cleaning relatively inconvenient.
The F series, however, comes with a detachable upper wheel, which greatly simplifies the cleaning process.

3. **Safety Protection**
The J series lacks anti-cutting protective gear.
The F series, by comparison, is outfitted with anti-cutting protective gear to enhance user safety during operation.