It's a standard 16" tube with auto 35mm length valve. STANDARD - doesn't mean ordinary: quality rubber compound combined with even wall thickness makes RFR tubes reliable and durable. RFR tubes were tested in laboratory!
For 16" tires
For tire width (ETRTO size in mm): from 47-305 to 57-305
Valve type: auto (Schrader / AV)
Valve length: 35 mm