The square design adds some weight to the rear of the club to help stabalize the clubface at impact, as well as enabling the depth (front to back) to increase by adding to the overall width of the club, thus keeping within USGA regulations of the depth to width ratio.
The only drawbacks to these clubs is that they tend to be a bit loud when striking the ball and you may lose a tiny bit of distance. But a small sacrifice in distance for an increase in accuracy is usually a good tradeoff.
The price on these may be a bit steep but there are a few pretty good clones on the market that sell for around $100. Check out:
GigaGolf XQ MUTO 460 Ti
Tour Series BLOC 455cc Driver
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