Despite the similarities with the Brazuca, the few differences between this ball and what players have gotten used to over the last four years will have an impact on play, says Firoz Alam, an aerodynamics engineer at the Royal Melbourne Institute of Technology in Australia, who has also performed wind tunnel tests on the Telstar 18. “When the player is making a short pass, they have to push a little harder, because at less then 60 kilometers per hour [or 37 miles per hour]it has more flight resistance than the Brazuca,” says Alam. The mid-range passes and corner kicks that gave the Jabulani so much trouble have been resolved. Compared to the Brazuca, the Telstar 18 is also more aerodynamically efficient in the 40-50 mile an hour range, so Alam says players will actually have to kick a little softer or they’re likely to overshoot. Over 55 miles an hour the two balls will feel very similar.
On the other hand, replicas (sometimes called training balls or gliders) are designed to be just like the official match balls but are much cheaper. Their panels are often stitched rather than thermally-bonded and are made of a different material. However, they’re not necessarily less durable than official match balls. So, they’re the recommended option for most players. https://www.youtube.com/watch?v=j2Xn84L3Kcs