Rotary Corp brand aftermarket product. Cast Iron Spindle Assembly Fits Bad Boy 037-4000-00, 037-4000-50. Old part numbers 037-8000-00, 038-4000-50. Fits Bad Boy Outlaw, Outlaw Extreme and Outlaw XP with 54", 61" and 72" Deck and Stand-on with 48", 54" and 61" Deck.