So far they're working great

For reference I am using these on inline skates, in particular I have them on Xsjados with Ground Control BIG frames and 72mm 84a wheels. Most of my riding is urban meaning on mixed surfaces of variable quality with frequent hops over small obstacles and on/off curbs with the occasional flight of stairs thrown in for good measure: rougher than a trail skating but not quite aggressive level rough. First of all I think the pricing is good; I haven't seen another set of 16 silicon nitride hybrid bearings available for this price. Onto the actual review:They come as two sets of 8 bearings including spacers. The spacers are the cylindrical 8mm kind (without flange), better suited to skateboards than inline skates, but will work for either (assuming the skates have 8mm axles). The packaging had oil stains on it so I presume the bearings are oil lubricated. In free spin they sounded a little less than smooth out of the box so I decided to clean/lubricate them.When cleaning I found what looked like a small piece of wire in one of them; I presumed this was manufacturing residue and could have been problematic. Once I cleaned/lubricated them (initially with light oil) the free spin on my wheels was around 90 seconds: much longer than with any of my all metal bearings.I rode them for about a week (about 1 hour per day) before taking them out again to inspect them. I cleaned them again which brought out "wire" pieces from a couple of the bearings. I assume this is part of the initial wear process where the races are reshaped by the balls. Since the shield had picked up quite a bit of dirt on it and a little of said dirt had made its way into the bearings I decided to use grease this time.I rode them for a couple of hours to get the grease worked in then cleaned off a little excess grease that leaked between the shield and inner race. Note that grease will considerably decrease your unloaded free spin time (to about 5 seconds in my case) but don't take this to mean it'll be slow in use; after the initial ride I didn't notice any appreciable speed difference in use compared to when lubricated with oil.They were relatively quiet with oil in any case (compared to all metal bearings) but using grease made them even quieter and, I suspect, keeps the dirt out better. Note that the retainer is nylon with the balls facing the closed side of the bearing: this means it would be harder to remove grease from them in a clean/relube compared to if they were mounted the other way around. Either way, a month on and I haven't relubricated them or noticed any noises or vibration developing or signs of increased resistance in use.In short I think these bearings are what you'd expect for the price: a serviceable low end hybrid bearing. If you are using them for inline skates with 8mm axles you may want to get some self centering spacers but they work fine with the ones provided once you get your axles through. Though I haven't tried, I'm sure they'd work fine on a skateboard too.

I used these to upgrade the wheels on my son's roller skates. The previous bearings were Bones "Super reds", which are about 30% cheaper or so. According to my son, he can tell the super reds are faster. Although that is subjective, the spin of the wheels is not. When you spin the super reds, each wheel continues turning for a little more than a minute. Even after breaking in the ceramic bearings, and using high-speed oil as per instructions, none of these will spin for more than about 20 seconds.

You can not beat these for the price. If you're looking to step up to ceramics without spending a fortune these are definitely worth it Very fast and smooth. Just bought them again for another set of skates.

Substituted a abec9 bearing set in my 10k reebok roller. So far it's rolling smooth, fast and quiet, I'll buy another brand to see how it compares to another leading brand such as swiss bones.

Sent back due to receiving item twice with only 8 not 16 bearings as stated in the description and title of product

Best bearings in terms of freespin imo