It is advised that passengers pack carefully and select luggage that does not exceed the dimensions of 22 x 18 x 10 inches. This includes rolling baggage, duffel bags, and backpacks that fit in overhead bins. Anything over these limits will have to be checked in, which could cause delays or additional fees. Those who follow Spirit's carry-on guidelines can benefit from expedited board... https://airlinesofficedesk.com/blog/spirit-airlines-carry-on-size/