Minecraft wiki entry for Hopper, associated text: 2/64 filter- plus 20 cheap items or 2/16 filter- plus 14 cheap items.
2
17
or
2
11
1-wide, alternating tileable, silent, transfer rate 2.5 ips.
protected against overflow chaos only when circuits "oh3-A" and "oh3-B" are mixed in alternating order (see notes below).