Long ago I found a needle reference chart on the net that listed many obsolete systems. This list went into much more detail of needle specs than just length ,diameter, etc. Unfortunately, I found it shortly before my computer died and I didn't have it in backup. Best I remember the 16x97 was much longer than any other 16 needle and again if memory serves it was much longer than other needles with the same or similar diameter. Someone once posted a page from this list here on the forum but I can't remember who or where. One of the dealers here on the forum may have this very list and be able to help with the specs.