I'm not sure what you're actually after though? When you refer to the "ideal one", I'm assuming you've had issues with needles in the past? Providing that they're new, sharp and the correct length - then you shouldn't be having any issues at all.
It might be worth looking for injection technique advice instead as I'd imagine that the majority (if not all) needles on the market should be of a decent standard.
I'm using the BD Micro Fine Ultra pen needles 4 mm and you can't get any smaller than that as I have asked that question and they are the only one that I feel comfortable with as I have used them all and they are the finest needle that is on the market up to date and I came to that size from the 5 mm ones as they were giving me a hypo every day and advised to change the needle size and I don't get as many now but I still get them though
Thanks for the feedback, everyone. I am currently using another make (Droplet) and they do not seem very sharp at times. So I have just ordered BD Micro Fine Ultra pen needles 4mm, hopefully they will work better for me.
I used to be on bd microfine ultra until it got discontinued in my area/surgery, but now use Agamatrix's TriCare 4mm needles (partnership with Owen Mumford) which are really good and flexible which are ultra thin, daresay thinner than bd microfine and had less bruises and bumps on skin whilst injecting.