Like the B-Band AST and the K&K Pure Mini, the LR Baggs I-Beam is a soundboard pickup that adheres to the inside of your guitar, on the bridgeplate between your soundhole and bridge pins. In doing so, it produces a remarkably natural tone by picking up the vibrations of the soundboard (rather than the vibration of the strings, as with undersaddle pickups). The I-Beam is responsive enough that it will even pick up percussive effects and fingersqueak. Included with each I-Beam is a placement jig that makes the pickup totally self-installable (provided you have the hole for the endpin jack in place). I-Beams are shipped with extra adhesive strips on request in case you need to experiment with placement.
Please note that the pickup listed here is the passive version of the I-Beam. I usually strongly recommend going with the active version of this pickup, which has an onboard battery and volume control. However, if you already have an outboard preamp like the Baggs Gigpro or PADI, then you may be able to get away with the passive I-Beam.
The Baggs I-Beam pickup is available in two versions, one for regular steel-string guitar and one for classical guitar. They are essentially identical, but the classical version has a little arch cut into the middle of the pickup so it can straddle the center fan brace.