Purchased 12 boxes of 4 each for my sister who uses a quad cane. She wears out 1 cane tip about every week or so and replaces 1 cane tip and rotates the others to wear more evenly. This is the brand she finds most stable and lasts the longest. She recently tried a different brand which also had a metal insert but the feel wasn't as sturdy.
Since we can't find them locally she needs to order them online. They are hard to find now, even from medical supply websites. Fortunately I could order them through Amazon and they arrived quickly. Only problem is the shipping for these is extremely expensive, not priced appropriately for multiple items. The items cost $45 and the shipping was $32.04 for a small box that wasn't very heavy.