Router question...

Folks,

I'm looking at routers, as I may have one bought for me as a combined birthday and Christmas gift from all members of the family!... (and have a new kitchen to fit in the spring, for myself, and possibly another later in the year)...
I'm looking at this one;
http://www.screwfix.com/p/hitachi-m12ve-j7-2000w-router-230v/87017

Can anyone advise the significance of the J7 in the name, as I've seen what appears to be the same elsewhere, but with either a J1, or J2 at the end?

Thanks in advance,

Regards,
Cando.