If this piece is cracked or brittle, serious water damage can occur. If you are planning to do a top installation yourself purchase any top WITH the rain rail your installation will go much smoother. If installation is to be done by a professional you can save money by using your existing rain rail if it is in good shape. The savings by not purchasing a rain rail needs to be weighed against the cost of a longer install time.
Roadstersport II was a great purchase, easy install, and sounds great.
I should thank you. The parts ordered have greatly enhanced my MX-5 and they were received well before I could have reasonably expected them. I'm an enthusiastic new customer. Regards, John
-- John W.