Use these to soften paint or anti-corrosion coatings which are fouling the the head you'll be attacking. Though the headline figures are similar these don't have the poke of full on induction heaters because a blast of hot air doesn't transfer heat as efficiently as direct induction. They will cause expansion and contraction of the fastener and/or shaft and help disrupt the corrosion. if used outside you must have appropriate electrocution protection.