Sensor without the measuring tube.
Often replacement MAFs are sold on an exchange basis as the new sensor is simply swapped into the old tube.
So, to avoid you having to return your old one for a surcharge this is just the sensor... swap it over, chuck your old one. Job done.
There are a few different MAFs used across the VAG Group, this one replaces the following VW Numbers (Found on the outside of your old MAF tube):
Most commonly found on VW T4 with ACV, AJT, AUF engines from '99 onwards.
These are supplied in a sealed bag, you open the bag, its yours forever... we will not accept returns if the bag is opened unless its faulty (which almost never happens with Pierburg products!)
In other words, don't buy it and expect to be able to just "try it" to see if it fixes your problem :)