Walbro in-tank pickups are great for fuel cells/tanks without internal baffles. They have 70 micron mesh that serve as a pre-filter. When the pickup is submerged in gas it draws through the mesh. The pickups hold small amount of gas when not submerged. When that small amount of gas is depleted the pickup will shut preventing the pump from sucking air. When the pickup becomes submerged again it will open to begin drawing gas again.
The pickups are usually run in quantities of 3 or 4 depending on the configuration. When there is a possibility of the fuel system being run completely dry, Walbro recommends running one pickup with a bleed in it.
The Walbro pickups have a 5/16" fitting on top. They are approximately 3" in diameter and 2" tall.