Here is a list of all the items that have been tested and confirmed to work with the SUB-2000 CQB:

• All Internal SUB-2000 Upgrades
• Rapid Deployment Latch (RDL)
• Buttstock Pad
• All 3 Charging Handle Options:
  
  • Double Finger Charging Handle
  • Recoilless Charging Handle
  • Skeletonized Charging Handle
• Bolt Tube Cover (It might be a little tight when folding the firearm but it fits)

Here is the Bad News...

Unfortunately the Muzzle Brake, Optic Mount, Rear Folding Sight and Shell Deflector will NOT fit/function with the KEL-TEC SUB-2000 CQB.