I have used this micro size 6 for 1/4" (ID) and 5/16" (ID) gas lines. I chose size 6 after asking a sizing question. As for the range, these clamps would go perfectly with both. Well, yes, they go with both, but not "quite well". You must order the smallest size for your application. This is because these clamps do not stay round when tightened, but rather take on a more oval shape, which clamps the hose on both sides rather than 360 degrees. I could have ordered a smaller size but I took aβ¦