About a year ago I picked up a Fender Fretless Jazz Bass (Jaco Signature) with a polyester coated, pau ferro fingerboard. I have tried several different sets of strings including TI Jazz Flats, DR Sunbeams and DA XLs. The TI's were probably the most unique sounding but not quite what I was looking for (too mellow). The Sunbeams and XLs yielded the classic 'roundwound' fretless sound particularly with the neck adjusted for minimal relief and low action. In a three piece lounge band situation, I found the roundwounds on the coated board were just too bright and lacking 'warmth'. I ordered a couple of sets of SM55s which took months to get but finally arrived recently. Being Rotos I added about half a turn of relief prior to installing them. They felt a little rough at first and I wasn't overly impressed with the sound of them but I played on. I am really glad I did! They are very 'playable' and rich sounding. They really respond well to good technique (and highlight poor technique equally as well). With full neck pick-up, the bridge pick-up backed off a quarter and playing over the board, I can produce a great, round tone perfect for slow blues and jazz standards (sort of 'uprighty'). Move my right hand closer over the neck pick-up and the tone tightens up nicely. Good for medium/up tempo shuffles. Full bridge pick-up, minimal neck pick-up and I can get a nice tight finger funk, almost Jacoesque tone. The harmonics are very clean and easy to get even in the lower register of the E string. The quality of the strings is average like the DRs and DAs but with tidy (green) silk windings. Not as nice as the TIs but they didn't cost as much either. I would recommend these strings highly for a fretless bass if your seeking something a little less 'aggressive' for a jazz/blues gig (but still want to cop a Jaco/Egan thing or two at the end of the night).