YES, the below HK parts will work perfect on a Cetme
Barrels Yes
Barrel Retainer Pins Yes
Firing Pin Yes*
Spring, for firing pin Yes*
Rollers Yes
+2, +4 Rollers Yes
Retainer Plate and Roll Pin Retainer for Rollers Yes
Extractor Yes*
Extractor Spring Yes*
Recoil Spring Yes*
Backplate or Complete recoil Assembly Yes with minor fitting to the plastic sleeve at the end of the spring guide rod
Complete Stock set Yes with minor fitting to the plastic sleeve at the end of the spring guide rod
Collapsible Stock Yes with minor fitting to the plastic sleeve at the end of the spring guide rod
Buttstock Yes with minor fitting (needs the buffer hole matched to use the cetme buffer)
Grip Frames Yes
Complete Trigger Pack Yes (but no individual parts)
Rear Sight Yes (but only if entire sight base is swapped)
Handguards, Slim Yes
Handguards Wide Yes with minor fitting. Just like the old style HK triple frame, the cetme has a bipod retaining ring that prevents the wide from installing
Pistol Grip Yes
Triple Frames Yes
Flash Hider Yes
Eyeloop for triple frame Yes
Cocking Handle Yes*
Spring for cocking handle Yes*
Pivot Pin for cocking handle Yes
Mag Catch parts Yes
Paddle mag release Yes
End Cap, Dust Cover Yes (but cetme will not fit g3)
Bayonet Adapter Yes*
Bayonet Yes* (only when using adapter)
Retainer Pins Yes*
Blank Firing Adapter Yes
Claw, Stanag Scope Mount Yes
POF Carry handle and Port Buffer Yes (carry handle slight modification to cetme handguard)

*these items not only interchange but are an improvement over existing Cetme parts.  Over the years some items have been strengthened or improved by HK.

No, the below HK parts will not work on a Cetme:
Trunions No
Bolt Carriers No
Locking Lever for bolt carrier No
Bolt Head No
Locking Piece No
Cocking Tube No
Support for Cocking Handle No
Recoil Buffer No unless using HK buttstock
individual fire control group parts like trigger, sear, hammer: No

	Cetme Bolt Head New stripped $45 (as pictured) Cetme Bolt Head New COMPLETE $55 (includes extractor, extractor spring, rollers, retainer plate and roll pin)
	Complete Cetme Full Auto Lower (Safe, Semi Full) New $90
	Paddle/Flapper Mag Release New $12
	Full Auto Hammer New $9
	Full Auto Trigger New $9
	Full Auto Sear New$9
	Sear Catch New $9
	Trip Lever New $9
	Bayonet Lug with cleaning kit/tube complete New $15
	Cetme Front Sight Tool, US made $11.75    (works better than the original Spanish tool!)
	Cetme Manual $5