The specification table on each product page lists cutting width or spread rate, power source and the size of the area it is meant to cover. Compare those figures against the item you are replacing rather than judging from the photograph.
This is the top level of the Lawn & Garden section: 5,928 items organised into subcategories so you can narrow down by product type before comparing specifications. Start from the subcategory that matches the job, then use the specification table on each listing to confirm the exact size or rating.
Orders over $39 ship free, and everything is dispatched within 1-2 business days.