For a 50-metre extension cable reel, the most important things to look at are cable thickness (mm2), load capacity, number of sockets, and safety features. The big decision is between 1.0mm (light duty) and 2.5mm (heavy duty) — this matters a lot for tools like welders, grinders, etc.
Best overall (heavy-duty, recommended)
Powermate 50M 2.5mm Heavy Duty Extension Reel
50 metres long
2.5mm2 copper cable (very important)
3–4 sockets
Overload protection + circuit breaker
Strong reel with handle