These 4 inch interchangeable knitting needle tips are made from Moso bamboo and are imprinted with the needle size. The 4" length tips can be used with an 8" cable to make a 16" circular needle. The join is nickel-plated copper. SPIN tips can be used with either SPIN Nylon Cables or TWIST Red Cables. The cables (sold separately) come in Small (S) and Large (L) join sizes. Tip sizes US2-US8 use the Small join cables and sizes US9 and above use the Large size cable joins.