The quad tuner and dual tuner ZapperBox have one USB 3.0 port, one USB 2.0 port and one microSD slot. You can see a 360-degree view of these models at this link. Scroll down to the second panel. The single tuner and Zapper Mini have one USB 2.0 port and one microSD slot.
The quad tuner has 128GB of built-in storage for DVR. The dual tuner and single tuner require minimum 128GB of added storage to get started with DVR. Do not add both USB and microSD storage. Only one can be used at any given time. There is no maximum drive size restriction. See FAQ #22 for more on supported drives. We recommend that the 60-minute pause buffer be disabled when using microSD cards and thumb drives that are slower than 400 Mbytes. This will help ensure a long life for such storage.
The Zapper Mini is not a DVR, it cannot record on its own storage. We call it a "tuner free DVR extender". You can attach storage from other ZapperBox DVRs to the Zapper Mini. This will allow you to watch clear (not encrypted) recording locally or share then with other devices.