The London Shubunkin Standard is as follows:
Depth of body to be approximately 40% of body length.
Caudal fin to be single and slightly forked with lobes slightly rounded at the ends. Depth of spread should be equal to depth of body and the leading edge should ideally be 25% of body length.
Dorsal and anal fins to be single, pectoral and pelvic fins paired and their extremities slightly rounded.
At least 25% of the body to be blue
Minimum body length to be 7.5 cm (3 inches).
The fish should be bright and alert. The body should be strong and sturdy with a smooth outline. The caudal fin should be short and slightly forked.
Colour:
Calico only (blue background with patches of violet, red, orange, yellow, brown and white, spotted with black). Quality fish should have a high intensity of colour evenly distributed over the body, with colour, especially black, extending into the fins.