PicoPen by TEC accesories

The PicoPen is a really small keychain pen. The cap with the small split ring is magnetic and that is what holds the pen inside the cap, no pressure or threading.

The pen comes in a very nice mettalic box with a nice set of accesories: a claw clip and a twisty keyring. The pen writes well and the small size and design is great for a keychain.

The magnetic cap is not a problem for credit cards or thumbdrives because the magnet is not very strong but can be used to attach the pen to some mettalic surfaces if you want.
You can get it for $20 from TEC website.