NPN phototransistor in clear 5mm transparent LED housing. 

Features:
- NPN Collector-to-Emitter Breakdown voltage: 30V
- Emitter-to-Collector Breakdown voltage: 5V
- Collector-to-Emitter Saturation voltage: 0.8V Max
- Rise and Fall time: 3uS @ 5V(Vce)
- Breakdown voltage: 5V
- Collector: Short Leg
- Emitter: Long Leg

See datasheet here.