With respect to @fandango68, there are a number of misstatements. This part appears correct:
Type 20 - Shamal Ultra, Eurus, Zonda and Neutron Ultra Wheels
Type 40 - Vento, Khamsin and Khamsin CX Wheels
Generic - everything else
I added links to stores that sell the first two types of skewers. I can't find a generic level of Campy skewer. Note that the wheels for the type 20 skewer are higher end than the wheels associated with the type 40s. Also, there is one higher-end class of Campy skewer supplied with their Bora, Hyperon, or Bullet wheels. I'll call these the Hyperon-level skewers.
From browsing Internet catalogs, the Type 20 and the Hyperon-level skewers are an internal cam design, meaning the cam mechanism that closes the skewer is shielded from elements. These produce greater clamping force for the same lever input than external cam skewers. The 40s appear to be external cam, as corroborated by this post on Velocipede Salon. External cam skewers can be made lighter than internal cams.
There are probably some material differences between all the levels of skewers, but I have not physically held any of them. I had one pair of Record skewers from the 10s era, about the mid 2000s. The cam housing, levers, and the rods were steel, (tested with a magnet). The nuts were aluminum. They were heavy but very pretty and functional. The current type 40s are aluminum nuts and levers with steel rods (also tested with magnet). The cam mechanisms should be steel. There may be differentiation between the level 20 and the top level skewers. For example, Shimano's Ultegra skewers have more plastic or other composite than the Dura Ace skewers, which are all aluminum except for the rods and cam mechanism.
External cam skewers are usually lighter, but they can get more easily contaminated, and they take more effort to close. Cheaper external cam skewers often use plastic nuts and levers, but I haven't examined the Campy level 40s.
Personally, I prefer internal cam skewers. Some reading is here, and more is here (paywall).
Last, this wasn't asked, but there are some points I wanted to address in the other answer. There is absolutely no reason to
... only use Campagnolo skewers on Campagnolo wheels...
Campy skewers will work with anybody's wheels, provided the hubs take quick release skewers. Although Shimano and Campy are long-time rivals, Shimano skewers will work with Campy wheels or vice versa, with aesthetic mismatch being the only consequence. Also, I haven't really seen this:
it's ridiculous to think a Campagnolo skewer is also marketed specifically to the number of cogs on your cassette - 9, 10 or 11 speed variations! It's just marketing spin.
In that context, people use the number of speeds like a model number. Shimano has explicit model numbers (e.g. DA 7700 is early 2000s, 9s Dura Ace), but Campy does not. However, if I said 10s Campy Record (like I did above), an educated consumer or mechanic would know that this refers to components from the early to late 2000s.
Since about 8-speed, road bikes have had 130mm dropout spacing. "8-speed" Campy skewers will work with any road bike that takes QR skewers that's been built since that era. Thus, that assertion is also incorrect. The worst that could happen is an aesthetic mismatch.
