Latest Firefox Mobile 21 user agents:

User Agent Platform Device
Mozilla/5.0 (Linux; ARMv7; Android 4.1.1; fr-fr; SonyEricsson Xperia E; rv 21.0) Gecko/20130514 Mobile Firefox/21.0 Android 4 Xperia
Mozilla/5.0 (Linux; Android 4.1.1; fr-fr; SonyEricsson; C1505 Build/11.3.A.0.56; rv 21.0) Gecko/20130514 Mobile Firefox/21.0 Android 4 Xperia E
Mozilla/5.0 (Android 7.0; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 7 Unknown
Mozilla/5.0 (Android 6.0.1; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 6 Unknown
Mozilla/5.0 (Android 4.2.2; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 4 Unknown
Mozilla/5.0 (Android 4.1.2; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 4 Unknown
Mozilla/5.0 (Android 4.0.3; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 4 Unknown
Mozilla/5.0 (Android 3.2.6; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 3 Unknown
Mozilla/5.0 (Android 2.2.3; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android 2 Unknown
Mozilla/5.0 (Android; Mobile; rv:21.0) Gecko/21.0 Firefox/21.0 Android Unknown