Maxitrol 20"-42" Black Spring BLK R13110, For RV131 / 210J Regulators20"-42" Black Spring For Maxitrol RV131 / 210J Regulators. Made in the USA. Product Specifications BRANDMaxitrol COLORBlack REGULATOR COMPATABILITYRV131 / 210J SPRING RANGE INCHES20 - 42 LIMITED WARRANTY YEARS1 MANUFACTURER'S PART NUMBERBLK R13110