Gotoh's GE101 range is an excellent line up of precision Japanese engineered hardware at a modest price point. Gotoh has established a reputation as one of the largest and most loved hardware manufacturers in the guitar industry for good reason. These stop tails are no exception to their exceptional track record.
There are two options (excluding the cosmetic plating) - zinc or aluminium. Zinc is heavier and lends itself to a greater sustain due to the increased mass. Aluminium is excellent for minimising the weight of a heavy instrument and making the instrument a little bit more percussive, and is more vintage accurate for those chasing a 50s tone.
Dimensions are found in the last product photo (dimensions are identical between the two materials, despite it being the zinc specification sheet).
See GE101-T stop tails for the other type of mounting post available.