diff --git a/Concept.md b/Concept.md
index c9e7eb0..04348d9 100644
--- a/Concept.md
+++ b/Concept.md
@@ -99,6 +99,7 @@ MB: Mashinebody
 C: Copper  
 R: Redstone
 HB: Heating Body  
+PI: Pressed Iron
 | . | 1 | 2 | 3 |
 | -- | -- | -- | -- |
 | 1 | HB | R  | HB |