Valentino Rossi is unsure if he will continue with Yamaha's new fairing, which made its public debut during Friday practice at the Thai MotoGP.

The factory, which pioneered the 'rail' wing design now used by most MotoGP teams, has pushed the boundaries further with its one available 2018 upgrade, which features a 'double wing' design, plus a diagonal support across a larger front opening.

Since it has been used in a grand prix weekend the design has been officially approved by technical director Danny Aldridge and, having been on track with the #46, now counts as Rossi's in-season update.

Team-mate Maverick Vinales is expected to try the new fairing, designed to help prevent wheelies under hard acceleration, at the Buriram circuit tomorrow.

However, Rossi felt little difference over the previous version.

"I tried the cowling and usually you are a little bit better for the anti-wheelie. But sincerely I don’t know if I will continue to use it, because it's very, very similar to the other one," explained the Italian, who was ninth fastest but only 0.3s from the top.

Normal exterior wings sticking out at 90-degrees are banned in MotoGP, but downforce devices are still allowed as long as they are 'integrated' into the fairing.

In practice, this has come to mean some form of 'rail', where the downforce section (wing) is attached to the fairing at either end and has no sharp edges in-between. But Yamaha is the first to 'stack' the sections.

It is not yet clear if the new Yamaha fairing would pass the stricter wing rules being imposed for 2019.