For old-school flats tone, these are great strings. To me, they sound good right out of the box. Of course with time they loose high-end and become even darker and thumpier. Perfect for Motown P-bass.
I eventually replaced them however, with Dunlop Stanless Steel Flatwounds. The Dunlops sound just about the same, especially when they are broken in, but are slightly less rigid and easier on the fretting hand. The Dunlops are now on the bass, and LaBellas in the drawer, for backup. This is only personal preference though, and the difference is really minor. I still highly recommend these LaBellas.