diff --git a/readme.md b/readme.md
index 0693bda..a4d645b 100644
--- a/readme.md
+++ b/readme.md
@@ -1949,13 +1949,13 @@ LMnUU linear bearings.
 | `bearing_groove_spacing(type)` | Spacing between grooves, outer to outer, ie includes the grooves themselves |
 | `bearing_length(type)` | Total length |
 | `bearing_rod_dia(type)` | Internal diameter |
-| `open_bearing_theta(type)` | For open bearings, the angle of the opening |
 | `open_bearing_width(type)` | For open bearings, the width of the opening at the rod |
 
 ### Functions
 | Function | Description |
 |:--- |:--- |
 | `bearing_radius(type)` | Outside radius |
+| `open_bearing_theta(type)` | For open bearings, the angle of the opening |
 
 ### Modules
 | Module | Description |
diff --git a/tests/png/bearing_blocks.png b/tests/png/bearing_blocks.png
index a014156..a5b93be 100644
Binary files a/tests/png/bearing_blocks.png and b/tests/png/bearing_blocks.png differ
diff --git a/tests/png/linear_bearings.png b/tests/png/linear_bearings.png
index aed602b..6128cd6 100644
Binary files a/tests/png/linear_bearings.png and b/tests/png/linear_bearings.png differ
diff --git a/tests/png/sbr_rails.png b/tests/png/sbr_rails.png
index 37051a1..d4c4108 100644
Binary files a/tests/png/sbr_rails.png and b/tests/png/sbr_rails.png differ
diff --git a/vitamins/linear_bearing.scad b/vitamins/linear_bearing.scad
index c8c1d38..d82b665 100644
--- a/vitamins/linear_bearing.scad
+++ b/vitamins/linear_bearing.scad
@@ -37,8 +37,8 @@ function bearing_groove_length(type)    = type[4];   //! Groove length
 function bearing_groove_dia(type)       = type[5];   //! Groove diameter
 function bearing_groove_spacing(type)   = type[6];   //! Spacing between grooves, outer to outer, ie includes the grooves themselves
 
-function open_bearing_theta(type)       = type[7]; //! For open bearings, the angle of the opening
-function open_bearing_width(type)       = type[8]; //! For open bearings, the width of the opening at the rod
+function open_bearing_width(type)       = type[7]; //! For open bearings, the width of the opening at the rod
+function open_bearing_theta(type)       = 2 * asin(open_bearing_width(type) / bearing_rod_dia(type)); //! For open bearings, the angle of the opening
 
 
 function bearing_radius(type)  = bearing_dia(type) / 2; //! Outside radius
diff --git a/vitamins/linear_bearings.scad b/vitamins/linear_bearings.scad
index 2791ecd..0f9b275 100644
--- a/vitamins/linear_bearings.scad
+++ b/vitamins/linear_bearings.scad
@@ -20,10 +20,10 @@
 //
 // Linear bearings
 //
-//                      L  od  id   gl    gd    gs   theta, h1
+//                      L  od  id   gl    gd    gs   h1
 LM16UU   = ["LM16UU",   37, 28, 16, 1.6, 27.0, 26.5];
 LM16LUU  = ["LM16LUU",  70, 28, 16, 1.6, 27.0, 53.0];
-LM16UUOP = ["LM16UUOP", 37, 28, 16, 1.6, 27.0, 26.5, 80, 11];
+LM16UUOP = ["LM16UUOP", 37, 28, 16, 1.6, 27.0, 26.5, 11];
 LM12UU   = ["LM12UU",   30, 21, 12, 1.3, 20.0, 23.0];
 LM12LUU  = ["LM12LUU",  57, 21, 12, 1.3, 20.0, 46.0];
 LM10UU   = ["LM10UU",   29, 19, 10, 1.3, 18.0, 22.0];
diff --git a/vitamins/sbr_rail.scad b/vitamins/sbr_rail.scad
index 4fba78f..7d8c31f 100644
--- a/vitamins/sbr_rail.scad
+++ b/vitamins/sbr_rail.scad
@@ -49,7 +49,6 @@ module sbr_rail(type , l) { //! Draw an SBR rail
     S3L = type[10]; // length of that screw
 
     h1 = open_bearing_width(sbr_bearing(sbr_rail_carriage(type)));
-    theta = open_bearing_theta(sbr_bearing(sbr_rail_carriage(type)));
 
     vitamin(str("sbr_rail(", d, ", ", l, "): SBR", d, " rail, length ", l, "mm"));