Hi all. I picked up a SR 405 bass at a pawn shop for $100 recently. I actually really like the sound of these pickups. I plan on doing a 4-string build, and would like to get the 4-sting equivalents. A few questions tho: 1. What are the topology of these things? Are they humbuckers? 2. Where can I get a set? I would be into purchasing a used set if anyone has them laying around... 3. If I cant find any, what are my other options? Are there any aftermarket companies that make a pickup with a similar sound and size? Thanks!