diff --git a/LEGO1/mxcriticalsection.h b/LEGO1/mxcriticalsection.h
index 8756853c..8c5f77d6 100644
--- a/LEGO1/mxcriticalsection.h
+++ b/LEGO1/mxcriticalsection.h
@@ -13,8 +13,8 @@ class MxCriticalSection {
 	void Leave();
 
 private:
-	CRITICAL_SECTION m_criticalSection;
-	HANDLE m_mutex;
+	CRITICAL_SECTION m_criticalSection; // 0x00
+	HANDLE m_mutex;                     // 0x18
 };
 
 #endif // MXCRITICALSECTION_H
diff --git a/LEGO1/mxdiskstreamprovider.cpp b/LEGO1/mxdiskstreamprovider.cpp
index dc2f7f94..c7e311eb 100644
--- a/LEGO1/mxdiskstreamprovider.cpp
+++ b/LEGO1/mxdiskstreamprovider.cpp
@@ -9,6 +9,7 @@
 #include "mxstring.h"
 #include "mxthread.h"
 
+DECOMP_SIZE_ASSERT(MxDiskStreamProviderThread, 0x1c)
 DECOMP_SIZE_ASSERT(MxDiskStreamProvider, 0x60);
 
 // GLOBAL: LEGO1 0x10102878
diff --git a/LEGO1/mxdiskstreamprovider.h b/LEGO1/mxdiskstreamprovider.h
index 6fc92d01..bc73c0e4 100644
--- a/LEGO1/mxdiskstreamprovider.h
+++ b/LEGO1/mxdiskstreamprovider.h
@@ -13,17 +13,17 @@ class MxDiskStreamProvider;
 class MxDSStreamingAction;
 
 // VTABLE: LEGO1 0x100dd130
+// SIZE 0x1c
 class MxDiskStreamProviderThread : public MxThread {
 public:
-	// Only inlined, no offset
 	inline MxDiskStreamProviderThread() : MxThread() { m_target = NULL; }
 
 	MxResult Run() override;
-
 	MxResult StartWithTarget(MxDiskStreamProvider* p_target);
 };
 
 // VTABLE: LEGO1 0x100dd138
+// SIZE 0x60
 class MxDiskStreamProvider : public MxStreamProvider {
 public:
 	MxDiskStreamProvider();
diff --git a/LEGO1/mxsemaphore.cpp b/LEGO1/mxsemaphore.cpp
index 18637185..5692a888 100644
--- a/LEGO1/mxsemaphore.cpp
+++ b/LEGO1/mxsemaphore.cpp
@@ -1,6 +1,10 @@
 
 #include "mxsemaphore.h"
 
+#include "decomp.h"
+
+DECOMP_SIZE_ASSERT(MxSemaphore, 0x08)
+
 // FUNCTION: LEGO1 0x100c87d0
 MxSemaphore::MxSemaphore()
 {
diff --git a/LEGO1/mxsemaphore.h b/LEGO1/mxsemaphore.h
index 3bc6d66b..ecb6509c 100644
--- a/LEGO1/mxsemaphore.h
+++ b/LEGO1/mxsemaphore.h
@@ -5,6 +5,7 @@
 
 #include <windows.h>
 
+// SIZE 0x08
 class MxSemaphore {
 public:
 	MxSemaphore();
@@ -18,7 +19,7 @@ class MxSemaphore {
 	void Release(MxU32 p_releaseCount);
 
 private:
-	HANDLE m_hSemaphore;
+	HANDLE m_hSemaphore; // 0x04
 };
 
 #endif // MX_SEMAPHORE_H
diff --git a/LEGO1/mxthread.cpp b/LEGO1/mxthread.cpp
index 899e959e..401860a1 100644
--- a/LEGO1/mxthread.cpp
+++ b/LEGO1/mxthread.cpp
@@ -1,11 +1,15 @@
 
 #include "mxthread.h"
 
+#include "decomp.h"
 #include "mxomni.h"
 #include "mxtimer.h"
 
 #include <process.h>
 
+DECOMP_SIZE_ASSERT(MxThread, 0x1c)
+DECOMP_SIZE_ASSERT(MxTickleThread, 0x20)
+
 // FUNCTION: LEGO1 0x100b8bb0
 MxTickleThread::MxTickleThread(MxCore* p_target, MxS32 p_frequencyMS)
 {
diff --git a/LEGO1/mxthread.h b/LEGO1/mxthread.h
index fa85b83d..e3af186d 100644
--- a/LEGO1/mxthread.h
+++ b/LEGO1/mxthread.h
@@ -8,6 +8,7 @@
 class MxCore;
 
 // VTABLE: LEGO1 0x100dc860
+// SIZE 0x1c
 class MxThread {
 public:
 	// Note: Comes before virtual destructor
@@ -18,7 +19,6 @@ class MxThread {
 	void Terminate();
 	void Sleep(MxS32 p_milliseconds);
 
-	// Inferred, not in DLL
 	inline MxBool IsRunning() { return m_running; }
 
 protected:
@@ -30,27 +30,26 @@ class MxThread {
 private:
 	static unsigned ThreadProc(void* p_thread);
 
-	MxULong m_hThread;
-	MxU32 m_threadId;
-	MxBool m_running;
-	MxSemaphore m_semaphore;
+	MxULong m_hThread;       // 0x04
+	MxU32 m_threadId;        // 0x08
+	MxBool m_running;        // 0x0c
+	MxSemaphore m_semaphore; // 0x10
 
 protected:
-	MxCore* m_target;
+	MxCore* m_target; // 0x18
 };
 
 // VTABLE: LEGO1 0x100dc6d8
+// SIZE 0x20
 class MxTickleThread : public MxThread {
 public:
 	MxTickleThread(MxCore* p_target, MxS32 p_frequencyMS);
-
-	// Only inlined, no offset
 	virtual ~MxTickleThread() {}
 
 	MxResult Run() override;
 
 private:
-	MxS32 m_frequencyMS;
+	MxS32 m_frequencyMS; // 0x1c
 };
 
 #endif // MXTHREAD_H