Currently, only one species, Trichoplax adhaerens, is acknowledged to belong to the Placozoa. The Italian Francesco Saverio Monticelli described another species in 1893, which he found in the waters around Naples, naming it Treptoplax reptans.
A standard mallet has a head length of 9 to 9.5, and this is recommended for beginners. Expert players may use longer head lengths up to 12, as this is thought to make aiming more accurate and makes it harder to accidentally twist the mallet during the stroke.
Racket size- Head size prevalent in professional tennis ranges anywhere between 95 and 105 sq inches, a larger head gives you a bigger sweet spot and fewer chances of a miss hit. Beam thickness- This is one thing that i have personally found important while playing but not given much importance while choosing rackets.