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This set is a replacement set of ankles for the recently released Krono's or 3rd party MP Skyfire/Jetfire. The two pegs included are to replace the peg that holds the two halves of the leg together in case it breaks during the removal process.
Update on the printed ankles: I decided to add some R/C diff lube to my shapeways ankles. Now it seem that they glide just a little too easy. He still stands without problems but I think the combination of the larger radii between holes and the lube is overkill. So my suggestion would be to NOT lube the shapeways versions unless you feel it is absolutely necessary.