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-ring at its base lets you attach weight to reduce the amount by which it swings, a useful addition for more intense routines.