Get this Patriot Viper Xtreme 4GB Desktop Module (Desktop) for $19.99 at Tiger Direct after sending in this $20 mail-in rebate. Shipping is around $4, varying by zip code. This is a low price for 4GB of computer memory by an estimated $19. This is 4GB in one DDR3-1333MHz module (PC3-10666). Check your PC's specifications on the type of memory you can install and how much you can add before purchasing. There is no sales tax (except FL, IL, NC, TX, GA, SD and ID).