Buttler uses a Shrey wicket keeping helmet - practically identical in design to the discontinued Masuri wicket keeping helmet - shorter peak (for a less interrupted view when looking upwards when a ball is top edged skyward) and a small portion of the back above the neck cut out (to avoid the back rubbing/hitting the neck when crouched in keeping position). Shrey have made very similar copies of other models like the Masuri fielding helmet as well.
He does bat in a Masuri Vision Elite for England.
On a side note, he seems to have stuck with the 2013 Masuri lid with Elite grill when batting for Lancashire - seems odd considering the new Vision series lid have been used and are available by e.g. Ashwell Prince, which seems to indicate he prefers the old style for county level.