From the Spector site:
"New from Stuart Spector Design, Spector Formula 603 Bass Strings!
Spector Formula 603 Stainless Steel Bass Strings are constructed of a stainless steel formula that delivers a crisp defined bright tone with a clear and tight low end. The lower tension of the Spector Formula 603 bass strings feel great for finger and percussive slap bass playing styles. Wound on a Hex core for consistent intonation and to minimize string twists. " $17 each shipped CONUS or $45 for all 3 sets
NOTE: No non-US buyers or alternate shipping addresses.