Are all front-side morrors the same or are there different specifications?

My local glass shop sells two different types of first surface mirrors, a cheaper one and a more expensive one. They apparently differ in quality. Also, I have seen the FS mirror of a disassembled 42 inches RPTV (a recent model) and it was made of a paper-like thin material streched evenly on a frame. Very light.

I bet that thin material was some kind of 3M reflective material, I think it reflects 99% instead of a normal mirror which is somewhere around 90% (I forget the exact number).

@japlasma
If you can find the efficiency (percentage of light they reflect) of the mirrors get the highest you can.

Take a look at Edmund Optical
They offer various coatings Aluminum, enhanced aluminum, gold (for IR) and multiple grades for the flatness and smoothness of the glass nothing is ever perfectly flat and the mirror can introduce distortion. You don't need scientific quality but you don't want it to thin, thicker will be more stable and a good surface. I think the mirrors start at something like 98-99% reflective but you can pay extra to get 99.99%. The standard quality is probably fine I'd suggest the thicker glass though.

Thanks a bunch guys for your input on this. I pulled a really big mirror from a rear projection TV and was just trying to figure out if, one, it's a FS mirror(I would think it's), second, what quality are they and third what size would I need for the LL Pro gear. My question now, how can I determine that this indeed is a FS mirror and the quality of it.
Thanks in advance.

It's actually quite easy to check if a mirror is a front surface mirror or not. Most likely, if both sides of the mirror seem to be equally reflective, then it's probably a front surface mirror. It's all in the name; "front surface mirror" means exactly that: the front surface is the mirrored surface. On a traditional mirror glass is the "front surface," meaning that there's a layer of glass between you and the reflective surface.

Just touch the glass with your fingernail. If it looks like the reflection of your fingernail is actually touching your fingernail then it's probably a front surface, if there's an obvious layer of glass between your fingernail and it's reflection then it is NOT a front surface.

Keep in mind that most household mirrors are not front surface mirrors, if you need a comparison mirror, just do the same test on the mirror in yo' bathroom.

Standard 4mm thick mirror from a average glass company will between 90% to 92% reflective e "Pilkington OptiMirror" is 92% reflective!