diff --git a/DCHdigi/include/DCHdigi.h b/DCHdigi/include/DCHdigi.h
index 317c3e3..1a438db 100644
--- a/DCHdigi/include/DCHdigi.h
+++ b/DCHdigi/include/DCHdigi.h
@@ -76,22 +76,17 @@
 /// constant to convert from mm (EDM4hep) to DD4hep (cm)
 constexpr double MM_TO_CM = 0.1;
 
-using colltype_in  = edm4hep::SimTrackerHitCollection;
-using colltype_out = extension::DriftChamberDigiV2Collection;
-using colltype_out2= extension::MCRecoDriftChamberDigiV2AssociationCollection;
-
-
 struct DCHdigi final
     : k4FWCore::MultiTransformer<
-          std::tuple<colltype_out,colltype_out2>(
-              const colltype_in&, const edm4hep::EventHeaderCollection&)> {
+          std::tuple<extension::DriftChamberDigiV2Collection,extension::MCRecoDriftChamberDigiV2AssociationCollection>(
+              const edm4hep::SimTrackerHitCollection&, const edm4hep::EventHeaderCollection&)> {
   DCHdigi(const std::string& name, ISvcLocator* svcLoc);
 
   StatusCode initialize() override;
   StatusCode finalize() override;
 
-  std::tuple<colltype_out,colltype_out2> operator()(
-      const colltype_in& ,
+  std::tuple<extension::DriftChamberDigiV2Collection,extension::MCRecoDriftChamberDigiV2AssociationCollection> operator()(
+      const edm4hep::SimTrackerHitCollection& ,
       const edm4hep::EventHeaderCollection&   ) const override;
 
 private:
diff --git a/DCHdigi/src/DCHdigi.cpp b/DCHdigi/src/DCHdigi.cpp
index 0e2f15e..5e00be4 100644
--- a/DCHdigi/src/DCHdigi.cpp
+++ b/DCHdigi/src/DCHdigi.cpp
@@ -97,8 +97,8 @@ StatusCode DCHdigi::initialize() {
 ///////////////////////////////////////////////////////////////////////////////////////
 ///////////////////////       operator()       ////////////////////////////////////////
 ///////////////////////////////////////////////////////////////////////////////////////
-std::tuple<colltype_out,colltype_out2>
-DCHdigi::operator()(const colltype_in& input_sim_hits,
+std::tuple<extension::DriftChamberDigiV2Collection,extension::MCRecoDriftChamberDigiV2AssociationCollection>
+DCHdigi::operator()(const edm4hep::SimTrackerHitCollection& input_sim_hits,
     const edm4hep::EventHeaderCollection&  headers) const {
 
     // initialize seed for random engine
@@ -107,8 +107,8 @@ DCHdigi::operator()(const colltype_in& input_sim_hits,
     debug() << "Input Sim Hit collection size: " << input_sim_hits.size() << endmsg;
 
     // Create the collections we are going to return
-    colltype_out output_digi_hits;
-    colltype_out2 output_digi_sim_association;
+    extension::DriftChamberDigiV2Collection output_digi_hits;
+    extension::MCRecoDriftChamberDigiV2AssociationCollection output_digi_sim_association;
 
     //loop over hit collection
     for (const auto& input_sim_hit : input_sim_hits)
@@ -185,7 +185,7 @@ DCHdigi::operator()(const colltype_in& input_sim_hits,
         }// end loop over hit collection
 
     /////////////////////////////////////////////////////////////////
-    return std::make_tuple<colltype_out,colltype_out2>(std::move(output_digi_hits),std::move(output_digi_sim_association));
+    return std::make_tuple<extension::DriftChamberDigiV2Collection,extension::MCRecoDriftChamberDigiV2AssociationCollection>(std::move(output_digi_hits),std::move(output_digi_sim_association));
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////