PVC Material Anti-burst Sister tool to the birth ball, a peanut ball can help with aligning your hips when you need or want to be in bed. Placing a peanut ball between your thighs while in a semi-reclined or side-lying position can facilitate a hip alignment that is similar to being upright. Alternate resting on the left and right sides, and being in a semi reclined position. ****Please note that our measurements are approximate. Based on level of inflation the size changes significantly. MEDIUM (Displayed turquoise/purple/green images) Most popular size, best suited to average size woman. Inflates from approx. 40cm x 90cm (can be inflated or deflated to work for most medium/tall body sizes) SMALL (Displayed as pink/blue in images) Best suited for petite woman. Inflates to approx. 30cm x 80cm (can be inflated or deflated to work for small/medium body sizes) In the pictures, Sue is 5'4" and is comfortable with either small or large peanut balls.