payed £80 for my cylinder full second hand from a dive centre (12.2 litre 232bar 5 years test 1st time tested) you have to mark the cylinder surface use only to get the full 5 years after testing, and if i could buy it again i'd pay the extra and get a 300bar tank as you get loads more fills to higher pressure well worth the extra upfront cost as both bottles cost £3 a fill at the same dive centre saving you the money in the long run also go for din fit rather than a clamp as i believe only din are meant to fill above 3000psi hope this helps