The sv1 cross fibre synthetic leather used in the carbon claw aero ax 5 4ft synthetic leather punch bag makes it strong durable and ideal for heavy boxing sessions this is enhanced by the heavy duty top cover zip and double stitched seams the punch bag is filled with compressed cloth material which supplies the resistance for your workouts and the 20mm foam lining gives good feel on every punch the 4 metal d rings and 4 heavy gauge webbing straps offer a secure way to fix the bag and the d