New York CNN Business  — 

Wendy’s highly anticipated new french fries are officially on sale — and they’re coming with a guarantee.

If you’re not happy with the fries, which have been reformulated to be extra hot and crispy, Wendy’s will replace them with no questions asked. Unsatisfied customers just have to bring them back to any of Wendy’s US locations for a free exchange.

The “Hot and Crispy Fry Guarantee” promotion is the chain’s way of raising awareness that its top-selling item is getting its first makeover in more than a decade.

“This guarantee is an expression of the trust we’ve built with our customers, assuring a high-quality, craveable experience every time,” Wendy’s Chief Marketing Officer Carl Loredo said in a release.

Wendy's new fries are here.

In August, Wendy’s exclusively told CNN Business about its fry transformation for the Covid era. The new recipe retains more heat and keeps fries crispier longer than its predecessor. The fries were revamped to improve the experience for customers who are shifting their ordering preferences to drive-thrus and delivery because of the pandemic.

The new fries look pretty similar to the old ones, but this time around Wendy’s has retained a bit more of the potato skin and is using a new batter system to ensure the heat and crispiness last longer. Wendy’s spent four years on the revamp, experimenting with 20 different shapes before landing on the new formula.

Wendy’s last changed its fries in November 2010, when it added sea salt and a natural “skin-on” cut. That was the first time the chain tweaked the fries since opening in 1969.

Wendy’s promotion is part of an increased marketing push for its popular food items. The company is spending an additional $10 million to advertise its breakfast menu this year, bringing its overall spending on breakfast ads to $25 million in 2021.