This is a ceramic slide made by Dunlop. Dunlop is well known as a quality manufacturer of a diverse array of products, from picks to pedals. There is a pretty uniform quality to all of their products and this is no exception to that track record.
The obvious defining characteristic of this slide it's the fact that it is made out of ceramic. Thus, it has a decidedly different sound from glass or brass slides. I'd say that overall, it's got a sound that isn't quite as bright as a glass slide. I find that on bright guitars, a glass slide is oftentimes far too bright for my taste and can be really harsh on the ears. This one has all the best characteristics of a glass slide, without the unnecessary high end. It also feels incredibly comfortable, this is due to the craftsmanship of the slide itself. It also has a design on the inside that is porous, and will absorb moisture from the finger to avoid slipping. This is crucial as a slippery slide is often problematic, and will cause the slide to slip off of the finger of the player, which, with a glass or ceramic slide, can easily result in breaking or cracking the slide.
While I'd say that this is probably not my favorite slide, I'd have to say it works better than most slides do on my Taylor 814ce, as that guitar is really bright. Thus, the duller, resonant sound works a lot better on it. I'm sure that there are a lot of other players out there who'd rather use the ceramic slide than glass, and in fact, I'd say that more often I'll use this than glass nowadays. It ends up coming down between brass and this one, and that's mainly a taste thing, and it depends just as much on what guitar I'm using.
Overall this is a great slide and I highly recommend it.