Compare the plug shapes, voltage and frequency in Cuba and Brunei, and find out which adapter you need before you travel.
Adapter required
Yes — coming from Cuba, you will need a travel adapter for Brunei. Cuba uses Type A/Type B plugs, and Brunei uses Type G, so the pin shapes will not fit any wall socket. Voltages differ (120 V at home vs 240 V abroad), so check the label on each device. Most modern dual-voltage chargers handle the swing without a converter, but heating appliances usually do not. The mains frequency is also different (60 Hz vs 50 Hz). This rarely matters for electronics but can affect motor-driven devices like clocks and shavers.
Cuba (home)
Brunei (destination)
Electrical specifications in Brunei
More about plugs in Brunei
In Brunei, the standard power plug is Type G. The country runs on 240 volts at 50 Hz. That means every wall socket in Brunei is the same shape — Type G, and your plug needs to physically match the socket to fit.
Full Brunei plug guide