Tubas are made with either piston or rotary valves. Mulching mowers use special mulching blades which are available for rotary mowers. Sheets are cut using saws and rotary cutting equipment. A hybrid between piston and rotary configuration is a double acting engine. Rotary or mechanical feedthroughs also exist. M61A1 is an example of an electrically powered rotary autocannon. Factories were fitted with overhead line shafts providing rotary power. Spool is of two types namely sliding and rotary. Membrane potentiometer manufacturers offer linear, rotary, and application-specific variations. This is the simplest of rotary positive displacement pumps. The shoe is common to both conventional combines and rotary combines. Some types of variable geometry craft transition between fixed wing and rotary wing configurations. Prior to the invention of the rotary snowplow ca. The FAA operates fixed wing and rotary wing aircraft. Mazda is also the only company to win with a rotary engine.