Block erupters can be the size of an usb stick. You can buy them on ebay for example, just look it up on google.
Think they are about 20 - 30 USD. I dont think they are profitable anymore.
Better buy a graphic card and mine scrypt based currencies.
yeah i see on ebay around 20-30 $ that's why i wanted to but around 10's + hub and start mining.
But is i will buy a GPU i need good mainboard and CPU as well ?