I've got a Steiner monocular 8x22 power porro-prismatic optics. It's over 10 years old and I've never had any problems with the quality.
http://www.hotbuyselectronics.com/steiner_monoculars_8x22_mini_scope_binoculars.htm(Mine's flat 'military' green color)
The 'porro-prismatic' part means when you unfold it, it only works along one sight axis. They're quite lightweight and the optics are quite good because they're Steiner.
My old Steiner 7X50 Military/Marine binos (with the compass) have lasted over 20 years with only a problem with the compass housing leaking damping liquid. I sent it back to them and they fixed it free except for the cost of shipping to the repair center. Those things have gone on almost every camping, hunting, fishing and road trips I've been through and since college so they've got some mileage and the optics still look great.
But, with the higer power monoculars it's really hard to hold still to use the full resolution quality they build in. You almost have to lay them down on something and move them around to find your subject. Steiner didn't seem to have them in their catalog that I could see and may not make them anymore. I paid about $200.00 and although they've been pretty good for the purpose, I wish I'd gone with the Zeiss model in the above posts. I'd probably go with the 4X12 model at the bottom of the next link if I were going with a dedicated monocular at that price point. An array:
http://www.bizrate.com/buy/products__att...--12180000.htmlPersonally, if buying ANY brand small, light optics like these, I'd go with lower magnification as you just can't really hold them still enough to use the higher magnifications - even your heartbeat shakes these light optics.
If I were going to spend that on a monocular these days, I'd spend a bit more and get the Zeiss monocular/adaptor for about $300. It works as its own 3x fogproof and water'proof' monocular and can be installed on your favorite Zeiss Classic binocular (my next optics purchase) to *triple* its magnification, effectively turning it into a spotting scope with magnification somewhere in the 21-30x power. Add mini-pod and you've got magnification from 3x to approx 30x in two quality items.