diff --git a/edm4eic.yaml b/edm4eic.yaml
index 0efd92c..9de1462 100644
--- a/edm4eic.yaml
+++ b/edm4eic.yaml
@@ -179,7 +179,18 @@ components:
       - int32_t           PDG             // PDG code
       - float             npe             // Overall photoelectron count
       - float             weight          // Weight of this hypothesis, such as likelihood, moment, etc.
- 
+
+  ## Representation of surfaces, including dynamic perigee surfaces (identical to ActsPodioEdm::Surface)
+  edm4eic::Surface:
+    Members: 
+      - int surfaceType                   // Cone = 0, Cylinder = 1, Disc = 2, Perigee = 3, Plane = 4, Straw = 5, Curvilinear = 6, Other = 7
+      - int boundsType                    // eCone = 0, eCylinder = 1, eDiamond = 2, eDisc = 3, eEllipse = 4, eLine = 5, eRectangle = 6, eTrapezoid = 7, eTriangle = 8, eDiscTrapezoid = 9, eConvexPolygon = 10, eAnnulus = 11, eBoundless = 12, eOther = 13
+      - uint64_t geometryId               // bit pattern volume:8,boundary:8,layer:12,approach:8,sensitive:20,extra:8
+      - uint64_t identifier               // identifier of associated detector element, if available
+      - std::array<double,10> boundValues // bound values, e.g. for RectangleBounds, BoundValues are eMinX = 0, eMinY = 1, eMaxX = 2, eMaxY = 3, eSize = 4
+      - uint32_t boundValuesSize          // size of bound values
+      - std::array<double,16> transform   // row-wise 4x4 affine transform [R T; 0 1] with 3x3 rotation matrix R and translation column 3-vector T
+
 datatypes:
 
   ## ==========================================================================