Review on 4-Pack 3.3V 5V FT232RL USB to TTL Serial Converter Adapter Module for Arduino by Daniel Russell

Adapters work properly. They come with no documentation except for the silkscreen on the circuit board, which is partially obscured by the components. One of the blocks I received had a broken jumper so it couldn't be configured to run on 3.3V. They're packaged as multiple blocks that are still connected together, so you'll have to snap the circuit boards together to separate them. (The circuit boards are notched for this purpose). One unit also had a small chipped circuit board under the USB ports that prevented the USB cable from being plugged in until I removed it.