Large Wiregates: Standard sized wiregates, ideal for virtually all climbing and particularly for technical mixed winter climbing where a lot of gear has to be placed and clipped whilst wearing gloves.
Micro Wiregates: Extra small krabs designed for situations where weight saving is more important than handling - eg high altitude mountaineering.
Solid Gates: Standard sized krabs with solid, rather than wire gates. These used to be the norm up until the late '90s and, despite being heavier than their wiregate equivalents, are still preferred by some climbers. However they are more prone to freezing up in winter and the gates tend to vibrate open and shut during a fall. They are particularly useful for wire racking as wires don't seem to unclip themselves from them quite so easily as they do with wiregates.