There are major differences between the engineering & construction names, Cramer said. If you're going to invest in the space, you've got to be careful.
"You need to know that this is a sector where a rising tide does not necessarily lift all boats," he said. "There are major differences."
Cramer explained that the latest earnings reports did a terrific job of separating the best from the rest.
For example, "Chicago Bridge & Iron is in terrific shape," he said.
When the company reported earnings in late February, "they knocked it out of the park," Cramer said.
Chicago Bridge & Iron had income of $89.6 million, or 91 cents per diluted share, compared with income of $70.5 million, or 70 cents per share in the same quarter a year earlier.
Analysts on average had expected a profit of 83 cents per share, according to Thomson Reuters I/B/E/S.