Please help!!

I need to replace my tyres soon, and I will replace them again with some BT023's.

Now in the owners book for the NCX it states:

Front: BT023F G 120/70ZR17M/C (58W)
Rear: BT023R G 160/60ZR17M/C (69W)

Now this is where I tumble, what does that 'G' stand for because I have two options on the following site.

http://www.tyres-pneus-online.co.uk/...X,BT,023,REAR/

On the above link I can buy the BT023 for 124.38 (SIZE: 160/60ZR17, 3rd from top) and that description has the 'Characteristic' of G against it or can I select the one that cost 113.18 (2nd from top) but the only difference is that it no longer states the 'G' characteristic (whatever that stands for) and has TL in the description instead which I presume stands for 'Tubeless'.

So the question is do I need to have the 'G' characteristic tyre or can i chose the other option?

EDIT: Just gone and had a look at my current BT023R's and the front states that it's of 'G' type but the rear doesn't state it, leaves me to assume that it's not of 'G' type so does it really matter?

The front is standard from the showroom when I picked the bike up but I had the rear changed by a garage to replace the original as it was worn.

Cheers for any help!!

Ash