Standard Pack = 1 piece(s). How To Size:The Largest motor on your machine must fall within the minimum and maximum range of the converterDo not order a Larger unit or Heavy Duty model thinking it will give more horsepowerWhen To Use Heavy Duty:Heavy starting loads (lathes, flyWheel driven equipment,etc.)Instant reversing, frequent starting, joggingAir compressors (motor pulley must be reduced by 1/3 IN Diameter)Heavily Loaded Equipment:For pumps, fans, blowers, direct-drive compressors, or equipment requiring greater than 2/3 of its rated HP, you must USE A PHASE-A-MATIC™ ROTARY CONVERTER.