Comments about Gitzo Gitzo 4.7" XL Spike Foot Set of 3, for Classic Monopods:

I originally bought the 1.5" spikes, but they just didn't give enough holding power. After I lost one of the 1.5's (I only put them on hand tight), I decided to buy the 4.7" (supposedly for monopods) They really do the job and hold so much batter than the 1.5's. They really increase the overall stability of the tripod when shooting on non-hard surfaces. The 1.5" spikes came with rubber feet that snap onto the spike, so I use them on the 4.7 spikes so that I don't have to remove the spikes when shooting on hard surfaces.

The only down side is the price. But for the $$ I paid for my carbon fiber GT3530, the feet are worth it for how they increase the stability.