This is a Cub Cadet Spacer Blade 748-3020. It fits 

Cub Cadet 208 (190-208-100) - Cub Cadet 44" Mower Deck - 44" Deck Drive & Spindle Assembly
Cub Cadet 2518-44 (13B-288L100, 13A-208L100)44 - Cub Cadet Garden Tractor - 44" Deck Drive & Spindle Assembly
Cub Cadet 364 (53AA1A5L100) - Cub Cadet Zero-Turn Mower - 44" Deck Assembly
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 GT2186-44 (13A-298L712, 13A-298L710) - Cub Cadet Garden Tractor - Deck Drive & Spindle Assembly 44"
Cub Cadet GT2544 (14A-2E7L010) - Cub Cadet Garden Tractor (2009 & After) - Deck Drive & Spindle Assembly 44 Inch.