watch nowCNBC's Jim Cramer on Tuesday explained why he think's Casey's General Stores has potential, saying the stock has more room to run."Last night, we got another terrific quarter from Casey's General, one of my absolute favorite under-the-radar growth stocks — you can buy this one and put it away," he said. "While the stock initially didn't react because management left their full-year forecast unchanged, I think they only did that because they feel it irresponsible to raise their guidance after just one quarter, as many companies do. They don't want to get ahead of themselves."Operating primarily in the Midwest and the South, the Iowa-based convenience chain sells a number of retail products including gas and hot food. Cramer said he thinks the company has found a great niche and has become "a spectacular regional to national growth story." Casey's intentionally targets smaller markets where their products can be a big draw, he said.Casey's posted an earnings and revenue beat on Monday. However, Cramer explained that some investors were disappointed that Casey's only maintained its full-year fiscal guidance despite a strong first quarter. Although the stock initially dipped early in the day, it finished Tuesday's session up 3.80%. Shares are currently up more than 36% year-to-date.Cramer said he wasn't deterred by the retailer's outlook. While he said he would have liked for Casey's to raise its guidance, he said it's standard for companies to maintain that metric after their very first fiscal quarter, unless results are extremely strong. Cramer was satisfied with the company's explanation for the unchanged outlook. The chain said it would reassess guidance after the next quarter once chain it's through the "seasonally largest time of the year."There were a number of aspects of the quarter that Cramer found impressive, including margin expansion and the successful rollout of new stores. He also pointed to positive commentary from management that he said suggests "behind its folksy veneer, this company is a very sophisticated operator." For example, he was encouraged by the results of its summer merchandising efforts, rewards member base, pricing strategy and ability to take market share in the fuel business without sacrificing margins."Everything's going great at Casey's, and the market eventually got this one right," Cramer said. "Still, after today's gains, you know what? I think there's much more upside to come."Casey's pointed CNBC to CEO Darren Rebelez's comments from the company's earnings release."Casey's delivered an excellent first quarter highlighted by strong sales growth both inside and outside the store," he said in the statement. "Our inside same-store sales were driven by positive traffic growth due to our summer merchandising plan as well as our team's outstanding execution, demonstrating our ability to serve our guests efficiently at a high level."watch now