The standard inner dimension for almost all pole tips is 12 mm. Some poles (Black Diamond) use a slightly narrower diameter (11 mm). If the tip you have to use is slightly loose, consider a turn or two of duck tape or gorilla tape to 'shim' the difference.
I always carry a partially roll of 1" Gorilla Brand Tape with me for all manner of repairs. This is one 'repair' that I often make for others who lose their original tips to the "mud god." or to wear.
FYI, I buy my pole tips (with inner metal 'washer') in bulk from Amazon. I regularly bring extras to hand out to others. This July, when I traveled to volunteer work at the Pilgrim Office in Santiago, I gave a large supply of these bulk purchase tips to the Pilgrim House for distribution to whoever needed them.
Check this URL to obtain these highly cost effective tips:
Amazon.com : Tebery 24 Pack Rubber Trek Pole Tip Protectors-11mm Hiking Pole Replacement Tips Fits All Standard Hiking, Trekking, Walking Poles : Sports & Outdoors
www.amazon.com
Hope this helps.