Commonly used for 25-series flash memory chips.

Exposed pins line the sides of the board, offering direct access to SPI, I2C, UART (TX/RX), and power lines for jumper cables.

Modern variants have fixed this, or hobbyists perform a simple track-cutting and soldering modification to force the data lines to 3.3V. The "Green Edition" or Multi-Switch Board

Basic versions are often "bare boards," but newer "all-in-one" versions (like the DSD TECH SH-U05A) come with protective casings for safer use. Common Use Cases

The "3 1" generally refers to three operational modes plus one voltage option (3.3V / 5V).