Here's what Seymour Duncan say about the STK-S7B:
The Vintage Hot Stack Plus is designed for the player who wants a little beefier tone, but does not want a high output pickup. The tone is bright and bouncy, but with just a little more of everything. Chords will feel more powerful, and single notes will ring through with just a bit more authority than they would with a vintage output single coil.
This pickup is designed to look like a traditional Strat single coil, and works great in neck, middle, or bridge position. And its dead quiet. Back in the 80s we patented a special bottom coil that actually injects negative hum into the pickup circuit and at the end of the production process, we fine tune each pickup for maximum noise cancellation.
Hand made in Santa Barbara, CA, the Custom Stack Plus uses alnico 5 rod magnets, a tappable 3-conductor lead wire, and is wax potted for squeal free operation.