diff --git a/Framework/ProcessSequence/ContinuousProcess.h b/Framework/ProcessSequence/ContinuousProcess.h
index c578f235244e62bb54729f3bf5d6014706c01fa9..32c1db6ab2832972b06a3dc86b37b90b74489578 100644
--- a/Framework/ProcessSequence/ContinuousProcess.h
+++ b/Framework/ProcessSequence/ContinuousProcess.h
@@ -13,6 +13,7 @@
 #define _include_corsika_continuousprocess_h_
 
 #include <corsika/process/ProcessReturn.h> // for convenience
+#include <corsika/units/PhysicalUnits.h>
 //#include <corsika/setup/SetupTrajectory.h>
 
 namespace corsika::process {
@@ -33,8 +34,12 @@ namespace corsika::process {
 
     // here starts the interface part
     // -> enforce derived to implement DoContinuous...
-    template <typename P, typename T, typename S>
-    inline EProcessReturn DoContinuous(P&, T&, S&) const;
+    template <typename Particle, typename Track, typename Stack>
+    EProcessReturn DoContinuous(Particle&, Track&, Stack&) const;
+    
+    // -> enforce derived to implement MaxStepLength...
+    template <typename Particle, typename Track>
+    corsika::units::si::LengthType MaxStepLength(Particle& p, Track& track) const;
   };
 
 } // namespace corsika::process
diff --git a/Framework/ProcessSequence/DecayProcess.h b/Framework/ProcessSequence/DecayProcess.h
index 076a32410495f8e7524b265284f7aa1d4f8417d5..0175cee60f8a4b8f8e0e4fd033cf07d64c239209 100644
--- a/Framework/ProcessSequence/DecayProcess.h
+++ b/Framework/ProcessSequence/DecayProcess.h
@@ -29,14 +29,13 @@ namespace corsika::process {
 
   template <typename derived>
   struct DecayProcess {
-
     derived& GetRef() { return static_cast<derived&>(*this); }
     const derived& GetRef() const { return static_cast<const derived&>(*this); }
 
     /// here starts the interface-definition part
     // -> enforce derived to implement DoDecay...
     template <typename Particle, typename Stack>
-    inline EProcessReturn DoDecay(Particle&, Stack&) const;
+    EProcessReturn DoDecay(Particle&, Stack&) const;
 
     template <typename Particle>
     corsika::units::si::TimeType GetLifetime(Particle& p) const;
diff --git a/Framework/ProcessSequence/ProcessSequence.h b/Framework/ProcessSequence/ProcessSequence.h
index d58c14b5083cfda5db73f468357fa28e38122248..3f0e357982c5741b3f80196fcb629410bc38f075 100644
--- a/Framework/ProcessSequence/ProcessSequence.h
+++ b/Framework/ProcessSequence/ProcessSequence.h
@@ -176,8 +176,9 @@ namespace corsika::process {
 
     template <typename Particle, typename Track>
     corsika::units::si::LengthType MaxStepLength(Particle& p, Track& track) const {
-      corsika::units::si::LengthType max_length =
+      corsika::units::si::LengthType max_length = // if no other process in the sequence implements it
           std::numeric_limits<double>::infinity() * corsika::units::si::meter;
+          
       if constexpr (std::is_base_of<ContinuousProcess<T1>, T1>::value ||
                     is_process_sequence<T1>::value) {
         corsika::units::si::LengthType const len = A.MaxStepLength(p, track);
diff --git a/Processes/NullModel/NullModel.cc b/Processes/NullModel/NullModel.cc
index 313d38034d3c90925eb461aa59b1399af8308e4d..4130bf0c4d5519408b272322dd45d60ee3b27b0e 100644
--- a/Processes/NullModel/NullModel.cc
+++ b/Processes/NullModel/NullModel.cc
@@ -1,4 +1,3 @@
-
 /**
  * (c) Copyright 2018 CORSIKA Project, corsika-project@lists.kit.edu
  *
@@ -11,37 +10,4 @@
 
 #include <corsika/process/null_model/NullModel.h>
 
-#include <corsika/logging/Logger.h>
-#include <corsika/setup/SetupTrajectory.h>
-
-#include <iostream>
-#include <limits>
-using namespace std;
-
-using namespace corsika;
-using namespace corsika::units::si;
-using namespace corsika::process::null_model;
-
-template <typename Stack>
-NullModel<Stack>::NullModel() {}
-
-template <typename Stack>
-NullModel<Stack>::~NullModel() {}
-
-template <typename Stack>
-process::EProcessReturn NullModel<Stack>::DoContinuous(Particle&, setup::Trajectory&,
-                                                       Stack&) const {
-  return EProcessReturn::eOk;
-}
-
-template <typename Stack>
-double NullModel<Stack>::MaxStepLength(Particle&, setup::Trajectory&) const {
-  return std::numeric_limits<double>::infinity();
-}
-
-template <typename Stack>
-void NullModel<Stack>::Init() {}
-
-#include <corsika/setup/SetupStack.h>
-
-template class process::null_model::NullModel<setup::Stack>;
+void corsika::process::null_model::NullModel::Init() {}
diff --git a/Processes/NullModel/NullModel.h b/Processes/NullModel/NullModel.h
index 367c907f38df5ab6b04bbc23ccaefc24a54df4ad..e1fc5b3ff8eaeeffdc5b6703f9dcc9f51516d87b 100644
--- a/Processes/NullModel/NullModel.h
+++ b/Processes/NullModel/NullModel.h
@@ -1,4 +1,3 @@
-
 /**
  * (c) Copyright 2018 CORSIKA Project, corsika-project@lists.kit.edu
  *
@@ -15,26 +14,29 @@
 #include <corsika/process/ContinuousProcess.h>
 #include <corsika/setup/SetupTrajectory.h>
 
-namespace corsika::process {
-
-  namespace null_model {
+namespace corsika::process::null_model {
 
-    template <typename Stack>
-    class NullModel {
+  class NullModel : public corsika::process::ContinuousProcess<NullModel> {
+    corsika::units::si::LengthType fMaxStepLength{
+        corsika::units::si::meter * std::numeric_limits<double>::infinity()};
 
-      typedef typename Stack::ParticleType Particle;
+  public:
+    NullModel(corsika::units::si::LengthType maxStepLength)
+        : fMaxStepLength(maxStepLength) {}
 
-    public:
-      NullModel();
-      ~NullModel();
+    void Init();
 
-      void Init();
-      EProcessReturn DoContinuous(Particle&, corsika::setup::Trajectory&, Stack& s) const;
-      double MaxStepLength(Particle&, corsika::setup::Trajectory&) const;
-    };
+    template <typename Particle, typename Track, typename Stack>
+    process::EProcessReturn DoContinuous(Particle&, Track&, Stack&) const {
+      return EProcessReturn::eOk;
+    }
 
-  } // namespace null_model
+    template <typename Particle, typename Track>
+    corsika::units::si::LengthType MaxStepLength(Particle&, Track&) const {
+      return fMaxStepLength;
+    }
+  };
 
-} // namespace corsika::process
+} // namespace corsika::process::null_model
 
 #endif
diff --git a/Processes/NullModel/testNullModel.cc b/Processes/NullModel/testNullModel.cc
index ffcba5e0351acefa519f6a28e003be7999741f68..56d635d1fafbf1806ed0a940985040934aa6a31d 100644
--- a/Processes/NullModel/testNullModel.cc
+++ b/Processes/NullModel/testNullModel.cc
@@ -43,11 +43,13 @@ TEST_CASE("NullModel", "[processes]") {
 
   SECTION("interface") {
 
-    NullModel<setup::Stack> model;
+    NullModel model(10_m);
 
     model.Init();
     [[maybe_unused]] const process::EProcessReturn ret =
         model.DoContinuous(particle, track, stack);
-    [[maybe_unused]] const double length = model.MaxStepLength(particle, track);
+    LengthType const length = model.MaxStepLength(particle, track);
+
+    CHECK((length / 10_m) == Approx(1));
   }
 }