diff --git a/AudioFilterConvolution_F32.cpp b/AudioFilterConvolution_F32.cpp
index f3fcc6b..b972171 100644
--- a/AudioFilterConvolution_F32.cpp
+++ b/AudioFilterConvolution_F32.cpp
@@ -25,6 +25,9 @@
   *******************************************************************/
   // Revised for OpenAudio_Arduino Teensy F32 library,  8 Feb 2022
   // Revised 18 January to work for Teensy 3.5 and T3.6.  Bob L
+  // Revised to be sure it will compile (run T3.5, T3.6, T4.x) for any. BobL 19 Jan 2023
+
+#if defined(__MK64FX512__) || defined(__MK66FX1M0__) || defined(__IMXRT1062__)
 
 #include "AudioFilterConvolution_F32.h"
 
@@ -278,3 +281,5 @@ void AudioFilterConvolution_F32::initFilter ( float32_t fc, float32_t Astop, int
     impulse(FIR_Coef);  // generates Filter Mask and enables the audio stream
 }
 
+// End Only T3.5, T3.6 or T4.x
+#endif
diff --git a/AudioFilterConvolution_F32.h b/AudioFilterConvolution_F32.h
index 35eac65..4b831f9 100644
--- a/AudioFilterConvolution_F32.h
+++ b/AudioFilterConvolution_F32.h
@@ -95,10 +95,13 @@
    * See the example TestConvolutionFilter.ino for more inforation on the
    * use of this class.
    *
+   * NOTE: This filter can be run under Teensy 3.5, 3.6, 4.0, 4.1 ONLY
+   *
    * Removed #defines that were not needed. Thanks K7MDL. Bob 6 Mar 2022
    * Separated Teensy 3 and 4 parts. Thanks Paul  Bob  16 Jan 2023
    *
    * ************************************************************ */
+#if defined(__MK64FX512__) || defined(__MK66FX1M0__) || defined(__IMXRT1062__)
 
 #ifndef AudioFilterConvolution_F32_h_
 #define AudioFilterConvolution_F32_h_
@@ -194,3 +197,6 @@ private:
 
 // end of read only once
 #endif
+
+// End T3.5, T3.6 or T4.x
+#endif
diff --git a/examples/TestConvolutinalFilter/TestConvolutinalFilter.ino b/examples/TestConvolutinalFilter/TestConvolutinalFilter.ino
index cae3ef7..30d1ac9 100644
--- a/examples/TestConvolutinalFilter/TestConvolutinalFilter.ino
+++ b/examples/TestConvolutinalFilter/TestConvolutinalFilter.ino
@@ -10,8 +10,11 @@
  * commented out.
  *
  *  Public Domain - Teensy
+ * Revised to only allow T3.5, T3.6 or T4.x  Bob L 19 Jan 2023
  */
 
+#if defined(__MK64FX512__) || defined(__MK66FX1M0__) || defined(__IMXRT1062__)
+
 #include "Audio.h"
 #include "OpenAudio_ArduinoLibrary.h"
 #include "AudioStream_F32.h"
@@ -117,3 +120,6 @@ void setup(void) {
 
 void loop() {
 }
+
+// End T3.5, T3.6 or T4.x
+#endif