Latest Fire OS 4 user agents:

User Agent Browser Device
Mozilla/5.0 (Linux; U; Android 4.4.3; pt-br; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.44 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; it-it; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.44 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; it-it; KFASWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.44 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Fire HD 7
Mozilla/5.0 (Linux; U; Android 4.4.3; it-it; KFARWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.68 like Chrome/39.0.2171.93 Safari/537.36 Mobile Silk 3 Fire HD 6
Mozilla/5.0 (Linux; U; Android 4.4.3; es-es; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.44 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; es-419; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.44 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFTHWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.67 like Chrome/39.0.2171.93 Safari/537.36 Mobile Silk 3 Kindle Fire HDX 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFTHWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.47 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HDX 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFTHWI Build/KTU84M) AppleWebKit/537.16 (KHTML, like Gecko) Version/4.0 Safari/537.16 Android Browser Kindle Fire HDX 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.48 like Chrome/39.0.2171.93 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.47 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.44 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFSOWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.41 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Kindle Fire HD 7" WiFi
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFASWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.68 like Chrome/39.0.2171.93 Safari/537.36 Mobile Silk 3 Fire HD 7
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFASWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.66 like Chrome/39.0.2171.93 Safari/537.36 Mobile Silk 3 Fire HD 7
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFASWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.47 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Fire HD 7
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFASWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.33 like Chrome/34.0.1847.137 Safari/537.36 Mobile Silk 3 Fire HD 7
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFARWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.48 like Chrome/39.0.2171.93 Safari/537.36 Mobile Silk 3 Fire HD 6
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFARWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.47 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Fire HD 6
Mozilla/5.0 (Linux; U; Android 4.4.3; en-us; KFARWI Build/KTU84M) AppleWebKit/537.36 (KHTML, like Gecko) Silk/3.45 like Chrome/37.0.2026.117 Safari/537.36 Mobile Silk 3 Fire HD 6