Hi, sorry for the delay!

I'm sorry the lumbar pack is no longer available. It may be because innov8 is designing more for fell running, and for that purpose, the newer designs--traditional running packs/vests but with the bladder secured at the bottom--are more effective. For inline skating the pack works fine, but when running it moves too much and the strap loosens.

On the bike I hardly notice it at all. It just sits there, it doesn't rotate or slip, I don't feel the weight or even think about it unless I need something from it. It's certainly not any more disturbing than fully packed jersey pockets. And it's practical for me to have the tools and such packed in one place so I can get out the door faster, regardless of which bike I take.

It holds a total of four liters, the bladder holds up to two liters and the rest is for whatever you want. If you don't use the space there is an elastic cord for compression on the outside, this also works for securing a rain jacket if the pack is full. (For example when hiking...) I usually take about a liter of water in the pack since 2 liters is actually pretty heavy, and if I drink that much I have to get rid of it at some point and then it's easy to refill it...

Since it's no longer available, I won't elaborate on the design, but lumbar packs are certainly work considering if you like having unrestricted breathing and having easy access to whatever you take with you.

Camelbak used to make some models that are often available on eBay...not a lot of people seem to be looking for them so you should be able to try one for very little money.