The Curt # C11435 is confirmed to fit your 2018 Mazda MX-5 Miata (ND). This is a Class I hitch with a 1-1/4" receiver. It has a maximum gross trailer weight of 2,000 lbs and tongue weight of 200 lbs. Make sure to consult your owner's manual for your vehicle towing/tongue weight capacity since it is likely the limiting factor. This features a bolt-on installation and a limited lifetime warranty. view full answer...
We do offer a Curt Class I hitch for your 2015 Mazda Miata MX-5 as long as it does not have the appearance package. It also fits the Miata with the power retractable hardtop. Curt hitch # C11028 features a 1-1/4-inch receiver opening and installs using included hardware. A bit of drilling and fascia trimming is required.
I have linked an install video as well as a helpful article to illustrate the installation process.
If you plan to use the hitch for a bike rack you can use one of the... view full answer...