Works for Me I’ve been using these pen needles for about a year and a half and have had no problems whatsoever. My old needles were 1/4″ and 6mm. These are much more comfortable to use. The needles insert smoothly and penetrate easily. There is an occasional “pop” as the needle penetrates the layer between the dermis and the subcutis, but this is not objectionable to me and it only happens infrequently. My only complaint is that these needles are about 40% more expensive than other brands.