You’ve probably seen bearings rated as Abec, Twincam and iLQ. Most people understand the framework of Abec ratings. Abec 9 is better than Abec 5, for example. The higher the number, the better the bearing (well, it’s actually not as clear as that but for arguments sake, that's the principle). But, skaters tend to be less clear about ratings such as 'Twincam' and 'iLQ'.
Twincam and iLQ are both brands that produce bearings together. They are the 'power couple' of bearing manufacturing and provide bearings for most of the brands on the market, including FR Skates, K2, Rollerblade and Powerslide.
If you see bearings not called Abec, Twincam or iLQ, it’s likely just a made-up name by the brand for a bearing that mimics the characteristics of an Twincam iLQ rated bearing. For example, Rollerblade have a "SG9" bearings.
Long-story short, Twincam iLQ bearings are industry standard high-quality bearings often being the best option for a majority of skaters.
So, what are the Twincam iLQ rated bearings and what might be right for you?
iLQ7
This is a 7 ball bearing often used in OEM skates. iLQ7 uses Japan Kyodo grease and is designed for recreational/urban skates for general everyday use. They will do the job pretty nicely for most people. This is the standard high quality general use bearing.
iLQ9 (or iLQ9 Classic)
This is an exclusive 6 ball bearing, which reduces friction and makes the bearing faster. They use a steel retainer (as opposed to rubber found in Abec) and the ball bearings are bigger than a 7 ball bearing at 2.4mm, making them stronger. The iLQ 9’s focus is for racing and long distance, so these will be good for skaters looking for extra performance in similar situations.
iLQ9 Pro
Similar to the iLQ9 the iLQ9 Pro is an exclusive 6 ball bearing, with an upgraded nylon retainer and is self lubricating. It uses 2.4mm ball bearings with an additional SCRS ring to avoid contamination entering. An ultra light gel is used for better inside shield protection. Designed for racing these will be good for skaters looking for extra performance in similar situations, slalom and wizard-style (and want the comfort of less grit/dirt entering the bearings).
iLQ Midget
The iLQ midget is not really found on the popular market. It is an exclusive 11 ball bearing which increases the spin force of the bearing. Composed of a nylon retainer, two sided rubber shield and ultra light gel the iLQ midget is designed specifically for track racing.
iLQ-X MR2
The iLQ-X MR2 bearings are 29% lighter than 608 bearings (like the others above). It is a 7 ball bearing with a noise reducing nylon retainer, also including an exclusive SCRS and DCF design. This is an additional ‘spacer’ that inserts into the central cavity of the bearing and sits on the outside (between the bearing and frame wall - Go Project Crown bearings use a similar system for reference). The iLQ-X MR2 have a really great connection with the frame wall and make skates feel more responsive. This will work well in most skating situations (though not optimised for track/racing).
SCRS Rustproof
Twincam Rustproof bearings are an excellent choice for skaters living in temperate climates, or regularly changing weather conditions. The components are designed to keep the bearing free from water contamination whilst self lubricating. They are not optimised for any particular discipline, but rather optimised for longevity. We find these bearings last a very long time and perform well at all tasks we've asked of it. Therefore the Twincam Rustproof bearings represent excellent value for money.
Beyond this it's common to see Twincam (not paired with iLQ) bearings called MW7 and MW9. These are very similar to iLQ7 and iLQ9 bearings just with slightly different components, making them very attractive to general use skaters.
Hope that helps!