Recently we posted about a new US based source for modded TCXO RTL-SDR dongles. Now Nooelec, one of the most popular sellers of standard RTL-SDR dongles have started selling their own version of TCXO modded dongles as well. Their dongles come with a 0.5 ppm TCXO oscillator as well as an external aluminium casing for interference shielding.
A TCXO is a temperature controlled oscillator. Its advantage over a standard oscillator like the one used in a normal RTL-SDR is that its frequency will not drift as the temperature of the dongle changes.