This is a Cub Cadet Zero Turn & 44A 44" Mower Deck Cup Spindle. For Tractor Models 365 365L 1000 1100 1200 1250 1450 1650 800. New Old Stock Part. Part No. 903-1387.   (39Cbx3)

Cub Cadet 365 (53CA1B6K100) - Cub Cadet Zero-Turn Mower - 54" Deck Spindle Assembly
Cub Cadet 365 (53CA1B6K100) - Cub Cadet Zero-Turn Mower (2001) - 54" Deck Spindle Assembly
Cub Cadet 365L (53CA1D5K100) - Cub Cadet Zero-Turn Mower - 54" Deck Spindle Assembly
Cub Cadet 365L (53CA1D5K100) - Cub Cadet Zero-Turn Mower (2001) - 54" Deck Spindle Assembly
Cub Cadet 44A - Cub Cadet 44", 3 Blade Deck (SN: 665000 & Below) - Mower Blade Drive