The Cold Steel .625 Big Bore blowgun is primarily compatible with Cold Steel accessories and darts specifically designed for the .625 caliber (approx. 16 mm). Since this caliber is larger than the standard of many other manufacturers, conventional darts often won't fit. When purchasing replacement parts, it's essential to check whether they are for the standard or professional series, as accessories like mouthpieces, quivers, and extensions are often only compatible with the respective model series. Third-party darts can be used, provided they are precisely tailored to the .625 caliber; users also report that standard Nerf darts, as a soft alternative, fit in the blowgun.