This is an adapter designed to allow the fitment of a 76mm internal diameter pipe/duct (very common on almost all reputable branded or eBay cold air intake kits) to the bulkhead of a Mk1 MX-5 / Miata / Eunos Roadster for a Randall cowl-style cold air intake. (If the Mk2 shares washer bottle mounts with the Mk1, it will fit those too!)
The STL included named "CUSTOM OFFSET ADAPTER" has been designed specifically to use the existing threaded holes in the bulkhead designed for the washer bottle to mount to, meaning that no extra holes need to be drilled aside from the single main hole for the intake to draw through.
I have this part mounted to my RHD 1.6 with Air Conditioning, and a strut tower brace. This combination has the least room in this corner of the bay due to the Freon piping for the AC, the brace limiting vertical and horizontal freedom of the air filter, and the larger AFM associated with the 1.6 compared to the 1.8's smaller MAF. If I was able to fit it given these circumstances, any other combination or spec should be a piece of cake!
The second STL, "BULKHEAD ADAPTER 2 BOLT" is a universal-style symmetrical adapter, in case you wish to fit a cold air feed elsewhere, or still have your washer bottle in the original spot for some reason.
If you have any questions don't hesitate to ask and I'll be happy to help!
Infill: 75% Layer Height: 0.20, or adjust to preference Material: ABS Support: No Raft: Yes