diff --git a/app-common/src/main/java/im/angry/openeuicc/core/DefaultEuiccChannelFactory.kt b/app-common/src/main/java/im/angry/openeuicc/core/DefaultEuiccChannelFactory.kt
index 5e87564..446611d 100644
--- a/app-common/src/main/java/im/angry/openeuicc/core/DefaultEuiccChannelFactory.kt
+++ b/app-common/src/main/java/im/angry/openeuicc/core/DefaultEuiccChannelFactory.kt
@@ -10,7 +10,11 @@ import im.angry.openeuicc.common.R
 import im.angry.openeuicc.core.usb.UsbApduInterface
 import im.angry.openeuicc.core.usb.getIoEndpoints
 import im.angry.openeuicc.util.*
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.runBlocking
 import java.lang.IllegalArgumentException
+import kotlin.math.max
+import kotlin.math.min
 
 open class DefaultEuiccChannelFactory(protected val context: Context) : EuiccChannelFactory {
     private var seService: SEService? = null
@@ -33,21 +37,23 @@ open class DefaultEuiccChannelFactory(protected val context: Context) : EuiccCha
         ensureSEService()
 
         Log.i(DefaultEuiccChannelManager.TAG, "Trying OMAPI for physical slot ${port.card.physicalSlotIndex}")
+
+        val verboseLoggingFlow = context.preferenceRepository.verboseLoggingFlow
+        val ignoreTLSCertificateFlow = context.preferenceRepository.ignoreTLSCertificateFlow
+        val maxSegmentSizeFlow = context.preferenceRepository.maxSegmentSizeFlow
+
         try {
             return EuiccChannelImpl(
                 context.getString(R.string.omapi),
                 port,
                 intrinsicChannelName = null,
-                OmapiApduInterface(
-                    seService!!,
-                    port,
-                    context.preferenceRepository.verboseLoggingFlow
-                ),
-                context.preferenceRepository.verboseLoggingFlow,
-                context.preferenceRepository.ignoreTLSCertificateFlow,
+                OmapiApduInterface(seService!!, port, verboseLoggingFlow),
+                verboseLoggingFlow,
+                ignoreTLSCertificateFlow,
             ).also {
-                Log.i(DefaultEuiccChannelManager.TAG, "Is OMAPI channel, setting MSS to 60")
-                it.lpa.setEs10xMss(60)
+                val mss = runBlocking { maxSegmentSizeFlow.first() }.toByte()
+                Log.i(DefaultEuiccChannelManager.TAG, "Is OMAPI channel, setting MSS to $mss")
+                it.lpa.setEs10xMss(mss)
             }
         } catch (e: IllegalArgumentException) {
             // Failed
diff --git a/app-common/src/main/java/im/angry/openeuicc/ui/SettingsFragment.kt b/app-common/src/main/java/im/angry/openeuicc/ui/SettingsFragment.kt
index fab680f..8f8c6b3 100644
--- a/app-common/src/main/java/im/angry/openeuicc/ui/SettingsFragment.kt
+++ b/app-common/src/main/java/im/angry/openeuicc/ui/SettingsFragment.kt
@@ -5,21 +5,26 @@ import android.net.Uri
 import android.os.Build
 import android.os.Bundle
 import android.provider.Settings
+import android.text.InputType
 import android.widget.Toast
 import androidx.lifecycle.lifecycleScope
 import androidx.preference.CheckBoxPreference
+import androidx.preference.EditTextPreference
 import androidx.preference.Preference
 import androidx.preference.PreferenceCategory
 import androidx.preference.PreferenceFragmentCompat
 import im.angry.openeuicc.common.R
 import im.angry.openeuicc.util.*
 import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
 
 open class SettingsFragment: PreferenceFragmentCompat() {
-    private lateinit var developerPref: PreferenceCategory
+    private val developerPref by lazy {
+        requirePreference<PreferenceCategory>("pref_developer")
+    }
 
     // Hidden developer options switch
     private var numClicks = 0
@@ -29,10 +34,8 @@ open class SettingsFragment: PreferenceFragmentCompat() {
     override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
         setPreferencesFromResource(R.xml.pref_settings, rootKey)
 
-        developerPref = requirePreference("pref_developer")
-
-        // Show / hide developer preference based on whether it is enabled
         lifecycleScope.launch {
+            // Show / hide developer preference based on whether it is enabled
             preferenceRepository.developerOptionsEnabledFlow
                 .onEach { developerPref.isVisible = it }
                 .collect()
@@ -57,6 +60,36 @@ open class SettingsFragment: PreferenceFragmentCompat() {
             intent = Intent(requireContext(), LogsActivity::class.java)
         }
 
+        findPreference<EditTextPreference>("pref_developer_max_segment_size")?.apply {
+            val mssFlow = preferenceRepository.maxSegmentSizeFlow
+
+            lifecycleScope.launch {
+                mssFlow.onEach { text = it.toString() }.collect()
+            }
+
+            setOnPreferenceChangeListener { _, newValue ->
+                // SGP.22 v2.2.2, 2.5.5 Segmented Bound Profile Package (Page 33 of 268)
+                // https://www.gsma.com/solutions-and-impact/technologies/esim/wp-content/uploads/2020/06/SGP.22-v2.2.2.pdf#page=33
+                //
+                // Each segment of this list that is up to 255 bytes is transported in one APDU.
+                // Larger TLVs are sent in blocks of 255 bytes for the first blocks and a last block that MAY be shorter.
+                text = runBlocking {
+                    val value = newValue as String
+                    when {
+                        value.isEmpty() -> mssFlow.removePreference()
+                        value.toInt() in 32..255 -> mssFlow.updatePreference(value.toInt())
+                    }
+                    mssFlow.first().toString()
+                }
+                false
+            }
+
+            setOnBindEditTextListener {
+                it.inputType = InputType.TYPE_CLASS_NUMBER
+                it.selectAll()
+            }
+        }
+
         requirePreference<CheckBoxPreference>("pref_notifications_download")
             .bindBooleanFlow(preferenceRepository.notificationDownloadFlow)
 
@@ -136,8 +169,8 @@ open class SettingsFragment: PreferenceFragmentCompat() {
     }
 
     protected fun mergePreferenceOverlay(overlayKey: String, targetKey: String) {
-        val overlayCat = requirePreference<PreferenceCategory>(overlayKey)
-        val targetCat = requirePreference<PreferenceCategory>(targetKey)
+        val overlayCat = findPreference<PreferenceCategory>(overlayKey)!!
+        val targetCat = findPreference<PreferenceCategory>(targetKey)!!
 
         val prefs = buildList {
             for (i in 0..<overlayCat.preferenceCount) {
diff --git a/app-common/src/main/java/im/angry/openeuicc/util/PreferenceUtils.kt b/app-common/src/main/java/im/angry/openeuicc/util/PreferenceUtils.kt
index f5e3ca2..14f90ce 100644
--- a/app-common/src/main/java/im/angry/openeuicc/util/PreferenceUtils.kt
+++ b/app-common/src/main/java/im/angry/openeuicc/util/PreferenceUtils.kt
@@ -5,6 +5,7 @@ import androidx.datastore.core.DataStore
 import androidx.datastore.preferences.core.Preferences
 import androidx.datastore.preferences.core.booleanPreferencesKey
 import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.intPreferencesKey
 import androidx.datastore.preferences.preferencesDataStore
 import androidx.fragment.app.Fragment
 import im.angry.openeuicc.OpenEuiccApplication
@@ -33,6 +34,7 @@ internal object PreferenceKeys {
     val DEVELOPER_OPTIONS_ENABLED = booleanPreferencesKey("developer_options_enabled")
     val UNFILTERED_PROFILE_LIST = booleanPreferencesKey("unfiltered_profile_list")
     val IGNORE_TLS_CERTIFICATE = booleanPreferencesKey("ignore_tls_certificate")
+    val MAX_SEGMENT_SIZE = intPreferencesKey("max_segment_size")
 }
 
 class PreferenceRepository(private val context: Context) {
@@ -50,6 +52,7 @@ class PreferenceRepository(private val context: Context) {
     val developerOptionsEnabledFlow = bindFlow(PreferenceKeys.DEVELOPER_OPTIONS_ENABLED, false)
     val unfilteredProfileListFlow = bindFlow(PreferenceKeys.UNFILTERED_PROFILE_LIST, false)
     val ignoreTLSCertificateFlow = bindFlow(PreferenceKeys.IGNORE_TLS_CERTIFICATE, false)
+    val maxSegmentSizeFlow = bindFlow(PreferenceKeys.MAX_SEGMENT_SIZE, 60)
 
     private fun <T> bindFlow(key: Preferences.Key<T>, defaultValue: T): PreferenceFlowWrapper<T> =
         PreferenceFlowWrapper(context, key, defaultValue)
@@ -66,6 +69,10 @@ class PreferenceFlowWrapper<T> private constructor(
         context.dataStore.data.map { it[key] ?: defaultValue }
     )
 
+    suspend fun removePreference() {
+        context.dataStore.edit { it.remove(key) }
+    }
+
     suspend fun updatePreference(value: T) {
         context.dataStore.edit { it[key] = value }
     }
diff --git a/app-common/src/main/res/values/strings.xml b/app-common/src/main/res/values/strings.xml
index 6c9fc34..3974a4b 100644
--- a/app-common/src/main/res/values/strings.xml
+++ b/app-common/src/main/res/values/strings.xml
@@ -164,6 +164,9 @@
     <string name="pref_developer_unfiltered_profile_list_desc">Include non-production profiles in the list</string>
     <string name="pref_developer_ignore_tls_certificate">Ignore SM-DP+ TLS certificate</string>
     <string name="pref_developer_ignore_tls_certificate_desc">Accept any TLS certificate used by the RSP server</string>
+    <string name="pref_developer_mss">Max Segment Size</string>
+    <string name="pref_developer_mss_desc">Update Max Segment Size</string>
+    <string name="pref_developer_mss_dialog_message">The valid max segment value range is from 32 to 255.</string>
     <string name="pref_info">Info</string>
     <string name="pref_info_app_version">App Version</string>
     <string name="pref_info_source_code">Source Code</string>
diff --git a/app-common/src/main/res/xml/pref_settings.xml b/app-common/src/main/res/xml/pref_settings.xml
index bb5bd50..63ef08a 100644
--- a/app-common/src/main/res/xml/pref_settings.xml
+++ b/app-common/src/main/res/xml/pref_settings.xml
@@ -69,6 +69,13 @@
             app:summary="@string/pref_developer_ignore_tls_certificate_desc"
             app:title="@string/pref_developer_ignore_tls_certificate" />
 
+        <EditTextPreference
+            app:dialogMessage="@string/pref_developer_mss_dialog_message"
+            app:iconSpaceReserved="false"
+            app:key="pref_developer_max_segment_size"
+            app:summary="@string/pref_developer_mss_desc"
+            app:title="@string/pref_developer_mss" />
+
     </PreferenceCategory>
 
     <PreferenceCategory