The 501LSW was developed to be used at the consumer level. The 502LSW was developed to be used in a pumping system at the manufacturing level. Very little difference with the exception of case quantity.
2016 Arctic Fox 25Y (For Sale), 2016 F350 4x4 DRW, 6.7
2008 Mobile Suites RE3: Sold
2005 Monaco Dynasty Diamond IV: Sold