diff --git a/README.md b/README.md
index 78224ef..7692e4b 100644
--- a/README.md
+++ b/README.md
@@ -4,10 +4,11 @@
 platformio run --target upload
 ```
 
-# Single strain half bridge
+## Single strain
 
-Single strain consiss of two 1k resistors voltage divider. Fitting two more
-fixed 1k resistors creates a full bridge. 50kg max.
+Individual strain consists of two 1k resistors connected as a voltage
+divider. Connection with two fixed 1k resistors as a voltage divider
+creates a full bridge. **50kg max.**
 
 ![Single strain half bridge with two additional 1k resistors
 breadboard view](./docs/1-strain_bb.jpg)
@@ -15,9 +16,10 @@ breadboard view](./docs/1-strain_bb.jpg)
 ![Single strain half bridge with two additional 1k resistors
 schematic](./docs/1-strain_schem.jpg)
 
-# Double strain half bridge
+## Double strain
 
-Using two single strain half bridges together forms a full bridge. 100kg max.
+Using two single strain half bridges together forms a full bridge. **100kg
+max.**
 
 ![Two single strain half bridges togerher breadboard
 view](./docs/2-strain_bb.jpg)
@@ -25,3 +27,13 @@ view](./docs/2-strain_bb.jpg)
 ![Two single strain half bridges togerher breadboard
 schematic](./docs/2-strain_schem.jpg)
 
+## Quadruple strain
+
+Using four single strain half bridges together again forms a full bridge,
+with the resistance doubled. **200kg max.**
+
+![Two single strain half bridges togerher breadboard
+view](./docs/4-strain_bb.jpg)
+
+![Two single strain half bridges togerher breadboard
+schematic](./docs/4-strain_schem.jpg)
diff --git a/docs/4-strain.fzz b/docs/4-strain.fzz
new file mode 100644
index 0000000..3f96e4e
Binary files /dev/null and b/docs/4-strain.fzz differ
diff --git a/docs/4-strain_bb.jpg b/docs/4-strain_bb.jpg
new file mode 100644
index 0000000..36cfa00
Binary files /dev/null and b/docs/4-strain_bb.jpg differ
diff --git a/docs/4-strain_schem.jpg b/docs/4-strain_schem.jpg
new file mode 100644
index 0000000..a1e4f6e
Binary files /dev/null and b/docs/4-strain_schem.jpg differ