SpeedOut: USB Speed Test
SpeedOut is a lightweight and free USB speed test tool built specifically for benchmarking USB flash drives. It accurately tests read and write speeds of USB drives, giving users a real world view of performance.
Flash Drive Benchmarking Software
USB Flash Drive Benchmarking Software and Bench Testing Tools
HDBench: Free Benchmark Software Utility
Another nice little Portable and Free Benchmarking Software Tool is HDBench. It can be used to quickly test and benchmark CPU, memory, video, and disk drive performance. Also, it works great for benchmarking USB flash drives. Although English language support is minimal, the Benchmarking Tool appears to work well and provides valuable insights into a system's overall performance.
Free Benchmark Software CrystalDiskMark
CrystalDiskMark is free benchmark software. You can use this free benchmarking tool to perform a USB speed test. Easily bench test the speed of your local hard drives, removable external USB flash drives, as well as even networked drives. In addition the utility supports drive speed testing through customizable profiles and even offers a NVMe SSD test option.