So I just ordered a CZ 455 to host my 22 suppressor on.  The description says it has a 11mm rail. Is this the same as a 3/8 rail? Will 3/8 inch rings fit on the 11mm dovetail.  I have only used "real" rail systems so I am not sure.

While I don't know for sure that they were 11mm rails, I have used standard 3/8 rings on several cz452.

I have a few cz's some 3/8 and some 11mm I have gotten adaptors to canvert to picatinny SWAF may have some I got mine from Dip products. the two rail size are differant and to get the best fit get the correct rings for the rail if you go for rings  without the picatinny adapter.

while the 3/8" and 11mm dovetails are not the same, there are some rings that will work for either.   THESE seem to be highly regarded by the CZ crowd over at rimfirecentral.com

I've a set knocking around that were previously mounted to my 452LUX. They worked nicely; I only removed so I could get back to using the tangent-style rear sights on my rifle.

My Anschutz sporter has an 11mm rail. I used these rings from champion shooters:
http://www.championshooters.com/store/product.php?productid=369&cat=274&page=1
They look much like the warne rimfire rings, but with an extra screw in the ring section.
They work very well for me. They never move, and they've not scratched either of the scopes I've mounted on the rifle at various times.
BTW OP: American or varmint for the suppressor host? I measured a 455 American barrel at a shop, and discovered that I wouldn't have enough shoulder behind the threads to mount my Spectre.

I ordered the 455 varmint.  I think the barrel is .866 and 20.5 inches long.  I an going to have it cut to 16 inches and threaded.  Friend of mine has one with his can and its ridiculously quiet with the bolt action.

I went through this a while back on a 452. Get a set that says 11mm / 3/8's, they worked.

11mm rings are the 'best' answer...

Or you can get a DIP 11mm to Picatinny rail.

There are 11 & 3/8th rings as well.

Be glad you don't have the 3/8 American rail... it's a little funky and there are quite a few ring sets that don't fit right. I bought the CZ rings for it which were somewhat pricey.

Measure the width of the top of the rail, if it is right at 1/2" it is a 3/8" dovetail.  If it is obviously under 1/2" then you have a 11mm dovetail.

My understanding is that the CZ rimfire rifles normally have an 11mm rail - while the "American" models of the  CZ 452 and CZ 453 used a 3/8" rail.   However, the CZ American uses an 11mm rail, standardizing it with other CZ 455s but also confusing the "American" issue somewhat.

The larger source of confusion however is that there are also exceptions to the use of 3/8" and 11mm rails with CZ apparently using what ever suitable 452 receiver that was available on some rifles.

The best advice is to just measure the rail on your particular CZ to see what is needs.

I also agree with the observation above that CZ's 3/8" rails can be very picky about rings - and it further adds to the confusion when a particular 3/8" ring does not fit, but then an 11mm ring fits even worse.