BJ Expert Arnold Snyder resonded to a similar question recently in a different forum (BJFORUMONLINE) and I'm going to reprint some of his response here and then append with some additional info of my own:
Assuming you have a locale where it is legal to use a concealable computer, you must still be very careful of knowing what you are buying before you purchase. If you are playing in multiple-deck games, do not purchase a "perfect strategy" computer. The most common types of these computers are usually sold under the name of "George." "David," or "Casey." These types of computers are very powerful in single-deck games, but do little more than regular card counting in shoe games. In fact, they would be a detriment in a shoe game because they make it difficult to table-hop.
For shoe games, and I'm talking about shoe games that are hand-shuffled, you would want a shuffle-tracking computer. The most common models are usually called "Thor" or No-Rand." I do not know if the older models of these computers will handle many of today's complex shuffles, and I know of no reputable sources for these computers. Thor was created by Keith Taft 20+ years ago, and was devastatingly powerful against the shuffles of that time, but Taft, to my knowledge, is no longer in the business of selling these devices. No-Rand was simply a bootleg of Taft's Thor computer, and worked the same.
I don't know of any pros using concealable computers today because of the legal status. The only computers I've seen being marketed recently are Caseys (a bootleg of Taft's David). Beware if the seller tries to convince you that these computers will beat shoe games. They will, but you'll actually do better with regular card counting just because you can move around easier.
The above siad, be clear that for all but the very best hidden computers, counting is almost as strong.
Now that said, if you were to use a hidden computer in the casino, a state-of-art hidden ROULETTE COMPUTER is FAR MORE POWERFUL.
You may examine that offering at the link below. zg
http://predictroulette.com
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