There are a few extra items that can be added to the basic P3Steel assembly that make its use more effective:
Small bed leveling thumbwheels (low profile)
These small low profile thumbwheels with an embedded M3 nyloc nut make bed leveling so much easier that they are considered almost essential (only 3 or 4 are needed, depending on the P3Steel frame version assembled).
Note that larger thumbwheels may not fit in the narrow space available under the P3Steel Y-carriage. These are tested and fit (Thingiverse 39459).
Front and back vibration dampening feet
If you use the P3Steel with its frame directly in contact with any surface you'll notice that it vibrates and rubs the surface, eventually wearing it. These small printed feet have been specifically designed to solve this problem (Thingiverse 532424).
Press the P3Steel frame firmly into the grooves of the feet to install them. Either a silicon or felt pad can be glued underneath.
Filament spool holder
Again, you can live for a short while without this part but sooner or later you are going to add it to your P3Steel!