BCS offers several options for Wheel Extensions, come as pairs.  All can improve stability on hillsides or rough terrain, or straddle garden beds, by increasing the overall wheel width of the BCS tractor.  Versions include:  
4.5'' (92243685)-$128.95
5.5'' (92243622) recommended for building raised beds with the Rotary Plow and Swivel Rotary Plow. 
16'' (922EX160) recommended to be used with the 4.5'' version to achieve a suitable width for straddling 30'' raised beds, particularly useful for the Plastic Mulch Layer.
22'' (16" plus 5.5" = 21.5") (922EX220) recommended to be used without any other extension to achieve a suitable width for straddling 30'' raised beds. 
 
Of course, any of the options above can be used to simply increase wheel width for additional traction and stability. 
 
The 4.5'' and 5.5'' Wheel Extensions can be stacked to further widen the wheel base.  Two sets of the 4.5'' Wheel Extensions can also be used to bolt dual wheels together for increased traction on the ground.