Bass and Guitar pickups usually require you to provide some pre-purchase information.  Please consider some or all of the following items in your comments.

1. Number of strings?
2. String spacing - center of string to center of adjacent string over the centerline of each pickup?
3. Single or dual coil?
4. If dual coil what options ?
5. Cover dimensions, route size, or pickup type?
6. New or existing instrument?
7. Will you be using a pre-amp?
8. Is the Magnetic pickup used with another pickup type (e.g. Piezo), and how will you blend the two?
9. Type of neck and body wood (please, no big details, just checking for plywood)?
10. Type of music you play?
11. What you´re hoping to achieve with an Aero verses some other pickup?