A great quality medium heat glow plug from Enya. If you slightly more Nitro and you find an Enya 3 is not delivering the top end R.P.M you think you should be getting then try a number 4. Often a Number 4 can increase the top end R.P.M without the tickover suffering. Try one and see.
Glow plugs are considered to be consumables - But by using a low voltage to start ( under 1.5 volts) and not burning the plug dry, you prolong the life of your glow plug. It is also worth washing out a new engine after running in to prevent small particles shorting the plug and destroying it. Blowing plugs on new engines is less common now a days, but is still something that can happen.