jeffjeeptj, the bottle I used was the standard one from the grocery store. I've used it on all Platypus bladders (1-3 liter) and the 750ml Lifeline bottles sold at Fred Meyer (a Kroger subsidiary) successfully (if you want, I'll provide a video showing this). It works on every 1 and 2 liter bottle I've tried it on (and even works by shoving it in to a wide mouth juice jug - something somebody wrote in their Amazon review - which took me by surprise). A coca-cola bottle will work (as will the Safeway brands and the company that makes Canada Dry tonic water). The only thing it has not worked well on is a 12 oz water bottle (threads weren't quite right, and the air tube is too long). Otherwise, I've never had a problem.
I've never tried it on a Sceptre bottle (actually, it wasn't until I started reading this thread about a year ago - after I submitted my patent application - that I even heard of Sceptre), but for the Nalgene bottles we've got something planned (part of the patent app), but it might be several years. Unfortunately, it doesn't fit on the Snap Cap well (the bottle cap that turns a Nalgene bottle into a smaller mouthed bottle).
PM me if you have any problems and I'll see what I can do to find a solution. Also, can you advise what specific Lifeline bottle you tried it on?
To all - the Simple Shower was designed for use with the ubiquitous 1 and 2 liter bottles that are sold worldwide, and then usually discarded - it's just been fortuitous that it fits other bottles (many of which I have found out by people saying "hey, do you think it'll fit...." and we try it, and behold, it does). I know it fits standard 1 and 2 liter bottles, Platypus bladders, and the Lifeline bottles I have tried. If you find others that it fits, please don't hesitate to let me know. And, if it doesn't fit a certain type of bottle (as jeffjeeptj points out with the Spectre bottle), please let me know that way, too. That way I'll be able to keep people apprised so they won't be disappointed).