I suggest the Leapers/UTG like one of these:
http://tinyurl.com/oe7rxnahttp://tinyurl.com/ousf2zkBoth are excellent, strong, look great and low cost.
The one piece no doubt only exist to hold on to springers, but those two piece are upgraded in strength so they're substantially stronger than common ones. I'd say just get whichever you like the looks of, but if you have an exceptionally abusive gun you can get the one piece and add two more screws to the clamp, which I've done and it's easy. I do it not for the extra grip, but for looks. But also for guns that don't have a hole for the stop pin and you don't want to add one, or you don't want to damage the hole. In that case you could skip the pin but have the extra grip of the screws.
You also need to decide what height you want. Most guns come with high rings which I think are ugly and upset your line of sight/trajectory. Medium rings are what I get but they often put the scope very close to the gun, usually not an issue but if you have to shim the scope then it can be. I'd still prefer to use med rings and mod the cover or gun as needed to use them, but up to you. And of course you need to get the correct 1" or 30mm to match.
Usually a 40mm AO or 44mm non-AO (including side adjust) is what's a close fit for med rings, but also the most popular sizes to get. If smaller then med will be fine, if larger than med will likely not work.
I attached a pix of a very popular UTG scope on a generic B18 to show people just that.
Also know that the height of med or high varies so no guarantee. I don't keep track but I have seen 5mm diff between high rings, much less with med but if you est 1mm clearance you may not get it when they arrive. High on the other hand are just too obnoxiously high imo me so I never use them. Yes that's 95% personal opinion so keep that in mind, many prefer the tall because it puts the scope at a better height for their eye.
The BLK are no doubt nice, but I doubt they hold as well and they're certainly much more $, like 4x? And do they even make medium?