they can be hard enuf to source.
there is also red and yellow tops in them, so you would need to buy to suit.
i have one and find it brilliant, its used for a jumpstart battery round the workshop and anything else that needs 12v power at times, i have had it for 7-8 yrs and its still perfect.
lately i found out that varta make the jd batteries so im buying them at the mo,
good quality battery from what it seems so far.
the varta are excellent in general.
i have a 10 yr old one in the jd and its still goin strong.
any other make of batterys available at the mo, from schnapp to dagenite are awful sh1te, ive got a few here just 18mths old and done.
the jd ones and especially the optimas might be dear but they are cheap in the long run imo.