These work exactly as expected. I tested data transfer speeds with and without the extension cable and there was no difference. Simple plug and play. They say not go longer than 10 feet for low speed devices and 16 feet for high speed devices. For kicks I plugged two cables in for a total of 24 feet (4 foot external hard drive cable plus two 10 feet extensions) and there was no speed difference or loss of data. If you need an extension, these work perfectly.