They are not transistors they are resistors and yes wrapping them with electrical tape would be fine. Another possible better option would be to insert one resistor then use heat shrink tubing on it then do the same on the next and then the final one so each resistor is covered in heat shrink tubing to protect it and prevent possible shorting between each other then to reinforce the entire setup you could use a larger piece of heat shrink tubing and cover the entire end and resistors as well to add strength to it and help prevent any possible shifting of the resistors since they are only friction fitted into the plug.