Spool type logic elements offered by Parker come in four basic variations with multiple sizes for each variation. Different sizes within each variation perform the same, but the larger the size (“_ _”) the more flow the valve is capable of passing. The advantage of using logic element technology is that high flows can be controlled using smaller pilot devices which can lead to more compact and efficient systems. Spool-type logic elements are typically used to control virtually any pressure or flow function since the spool is allowed to modulate. However, spool valves have clearances, so Parker also offers Poppet-Type logic elements for high flow 2-way, 2-position low leak requirements.