Which tack item is used specifically to provide better stability and security for the rider?

The correct choice is the Western saddle. This type of saddle has a distinctive design that includes a higher cantle and a wider seat, which contribute to a stable and secure riding platform for the rider. The structure of the Western saddle is specifically made to allow the rider to feel more secure while riding, particularly during movements that require turning or sudden stops, and it typically provides better weight distribution across the horse's back.

In contrast, while thigh rolls can enhance stability to some degree by allowing riders to grip the saddle more effectively, they are not as fundamental to the overall stability of the rider as the design of the Western saddle. A dual girth system is used primarily for girth adjustment and does not inherently increase rider stability. Lastly, a cavesson serves a different function related to bridle and control rather than rider security and stability.