clark engineering limited

does exactly what you would want of a bubble and more, its accurate and is self calibrating, it does you're basic three things a level on both axis of the phone, a full 3D bubble when you're phone is placed on its back horizontally, and my favourite feature is when level hits naught you get a audio bleep which is super handy for when you're trying to level something and maybe cant use you're eyes due to maybe the position of the job or when you want a job to be dead accurate rather than trying to approximate when the bubble is smack in between the lines which usually has a gap either side of