diff --git a/GUI/Model/Device/InstrumentItems.cpp b/GUI/Model/Device/InstrumentItems.cpp
index 990cfa969a14051698aa2477f0999eeebc598fc3..e7251929683e73088f7936182337ba4955f99bc5 100644
--- a/GUI/Model/Device/InstrumentItems.cpp
+++ b/GUI/Model/Device/InstrumentItems.cpp
@@ -57,11 +57,16 @@ InstrumentItem::InstrumentItem()
     : m_withPolarizerAnalyzer(false)
 {
     m_id = QUuid::createUuid().toString();
-    m_analyzerEfficiency.init("Efficiency", "", 0.0, Unit::unitless, 3, RealLimits::limitless(),
-                              "efficiency");
-    m_analyzerTotalTransmission.init("Transmission", "", 1.0, Unit::unitless, "transmission");
-    m_polarization.init("Polarization", "", Unit::unitless, "polarization");
-    m_analyzerDirection.init("Analyzer direction", "", Unit::unitless, "analyzerDirection");
+    m_analyzerEfficiency.init("Analyzer efficiency", "Efficiency of the polarization analysis", 0.0,
+                              Unit::unitless, 4, RealLimits::limitless(), "efficiency");
+    m_analyzerTotalTransmission.init("Analyzer transmission",
+                                     "Total transmission of the polarization analysis", 1.0,
+                                     Unit::unitless, 4, RealLimits::nonnegative(), "transmission");
+    m_polarization.init("Polarization (Bloch vector)",
+                        "Polarization of the beam, given as the Bloch vector", Unit::unitless,
+                        "polarization");
+    m_analyzerDirection.init("Analyzer direction", "Direction of the polarization analysis",
+                             Unit::unitless, "analyzerDirection");
     m_background.init<BackgroundItemCatalog>("Background", "", "background");
 }
 
diff --git a/GUI/Model/Device/RectangularDetectorItem.cpp b/GUI/Model/Device/RectangularDetectorItem.cpp
index 8c3b1d12501f657ad9961a1eacf3f8253abc1dfc..48727a2a20a89595b59c64d9dd240354a482dfff 100644
--- a/GUI/Model/Device/RectangularDetectorItem.cpp
+++ b/GUI/Model/Device/RectangularDetectorItem.cpp
@@ -75,9 +75,14 @@ RectangularDetectorItem::RectangularDetectorItem()
     m_height.init("Height (y-axis)", "Height of the detector", default_detector_height, "mm", 3,
                   RealLimits::positive(), "height");
 
-    m_normalVector.init("Normal vector", "", Unit::unitless, "normalVector");
+    m_normalVector.init(
+        "Normal vector",
+        "Normal of the detector plane with length equal to the sample detector distance",
+        Unit::unitless, "normalVector");
     m_normalVector.r3().setX(default_detector_distance);
-    m_directionVector.init("Direction vector", "", Unit::unitless, "directionVector");
+    m_directionVector.init("Direction vector",
+                           "Detector axis direction vector w.r.t. the sample coordinate system",
+                           Unit::unitless, "directionVector");
     m_directionVector.r3().setY(-1.0);
 
     m_u0.init("u0", "", default_detector_width / 2., "mm", 3, RealLimits::limitless(), "u0");