Because the ball diameters are different

56" (142 cm) from the bottom of the pannier

Back protector constructed in three waist-to-shoulder dimensions in order to cover all body sizes

Protects backbone in the event of a fall

Upper arm snap adjustment

GPR Exhaust - Albus Ceramic Racing Slip-On for Aprilia SX 125 - 2018 to 2020 Muffler with:Link Pipe-Dbkiller Because the ball diameters areThis kit includes the specific link pipe or half manifold with specific appropriate brackets and accessories. This allows for installation without any structural modifications. Technical Specifications Shape: Oval Body Color: White glossy Endcap Color: White glossy Body Length: 350mm or 13. 78 inches Weight: 1. 74kg or 3. 84 lbs Removable DBKillers?: Yes Removable GPR Catalyser?: NO Product Information RACING PRODUCT: This exhaust is supplied with a