I no longer have an 18” WSM to test fit, but I’m going out on a limb to say yes it’ll fit. Do you intend to grill on the existing lower and upper grates of the mid-section? Or drop an 18” grate into the bowl?
Slow ‘N Sear charcoal basket will work on an 18” WSM. I did test fit SnS char basket in my 20 year old WSM.Slow ‘N Sear Deluxe (2.0) will not fit inside an 18” WSM.See attached pic for dimensions. CheersThanx for this information.Sent from my iPhone using Weber Kettle Club