Use: To get a different voice from my main horn (bass trombone) for homemade videos and such
The SL-39's quality is good for this price range. The slide is not perfect and requires decent amount of slide lubricant to get it moving acceptably, although still around 7/10. However, the overall build quality is good, an the assembly is solid and clean. It is quite front-heavy, which is not so good for any trombone, but not that severe and I think I will try fix it myself with homemade solution (like taped weight).
I cannot say much about the intonation and sound, since this is my first alto experience. However, it does sound like ones I have heard others played before, and the intonation quirks, while present, are easy to adapt to. The case is also compact and lightweight. Overall I am satisfied with the purchase.
***I test it with GEWA 7C mouthpiece, not the one that came with the horn.
Pros: Good overall build quality, good value for price, nice case and supplements
Cons: Slide is not perfect, a bit front heavy