We at 3B Tech provide custom DVR units based on award winning GV capture cards. A common question our customers ask is how much hard drive space they will need. The following interactive chart should give you a good estimate as to recommended hard drive sizes. Please contact us at 877-328-3248 or e-mail sales@3btech.biz if you have any questions, or if you would like a quote on security capture cards, DVR units, cameras, or installation services.