All included parts are in the first pic
you need to add:
the small barrell spring (if you decide to install one)
Hop rubber
Hop rubber nub
Brass barell shim ( i dont know what you call this item, the small brass ring that slides over your barell)
I have only tried them in G&P 'complete guns' and my own builds, which tend to be G&P/SYSTEMA etc
I have one Dboys mechbox in a King arms gun that i was going to install one to, but i am awaiting some more barell springs (will update later)
it seems to work perfectly with everything i have thrown at it, it is built for a TM pl