The boys from Geneva have created what i consider the most advanced mallet head to date. Now, if you think that looks a helluva lot like the Milwaukee heads sold at Benscycle, you'd be right, but the Geneva guys even say (here) that they learned of the material and were inspired by the MKE mallets. But whereas the MKE heads are lathed UHMW tubing, the MILK heads are CNC'd UHMW rod.
This allows integrated "caps" and a reinforced center near the shaft.
They even made a custom shaft that fits like a glove into the new heads.
At $25 for the head and $25 for the shaft (plus shipping for Switzerland) these are a little pricey, but you get what you pay for, and if you want the most advanced mallet on the poloverse, this is it!
I have a bike to build, but you better believe i'm ordering one of these things the moment i have the money.
...and they made a video too!
buy MILK mallets here.