Download the 2017 Rules here:

HJL Rules 2017

The ECB and PCA strongly encourage all cricket clubs and cricketers to review their existing head protector equipment. In this Guidance Note, references to “head protectors” means helmets with a faceguard or grille.
The design and manufacture of cricket head protectors is now governed by British Standard BS7928:2013, which has been adopted by the ICC as the international standard. The standard ECB/PCA playing contract for professional cricketers also specifies that any helmet provided to a player by his employer club must meet this safety standard.
Note that BS7928:2013 specifies different tests for helmets to be used in senior and junior cricket, reflecting the smaller ball size used in the latter.

The rules for the Summer competitions will be the same as those for the U11 11-a-side, U13 and U15 mixed competitions with the following exception:

Players at all age groups will be required to retire at 25 and no one bowler will be allowed to bowl more than 3 overs.