diff --git a/cherryusb_config_template.h b/cherryusb_config_template.h
index 008ff921..f515099b 100644
--- a/cherryusb_config_template.h
+++ b/cherryusb_config_template.h
@@ -145,21 +145,24 @@
 #endif
 
 /* This parameter affects usb performance, and depends on (TCP_WND)tcp eceive windows size,
- * you can change with 2K,4K,8K,16K,default is 2K to get one TCP_MSS
+ * you can change to 2K ~ 16K and must be larger than TCP RX windows size in order to avoid being overflow.
  */
 #ifndef CONFIG_USBHOST_RNDIS_ETH_MAX_RX_SIZE
 #define CONFIG_USBHOST_RNDIS_ETH_MAX_RX_SIZE (2048)
 #endif
+
+/* Because lwip do not support multi pbuf at a time, so increasing this variable has no performance improvement */
 #ifndef CONFIG_USBHOST_RNDIS_ETH_MAX_TX_SIZE
 #define CONFIG_USBHOST_RNDIS_ETH_MAX_TX_SIZE (2048)
 #endif
 
 /* This parameter affects usb performance, and depends on (TCP_WND)tcp eceive windows size,
- * you can change with 2K,4K,8K,16K,default is 2K to get one TCP_MSS
+ * you can change to 2K ~ 16K and must be larger than TCP RX windows size in order to avoid being overflow.
  */
 #ifndef CONFIG_USBHOST_CDC_NCM_ETH_MAX_RX_SIZE
 #define CONFIG_USBHOST_CDC_NCM_ETH_MAX_RX_SIZE (2048)
 #endif
+/* Because lwip do not support multi pbuf at a time, so increasing this variable has no performance improvement */
 #ifndef CONFIG_USBHOST_CDC_NCM_ETH_MAX_TX_SIZE
 #define CONFIG_USBHOST_CDC_NCM_ETH_MAX_TX_SIZE (2048)
 #endif