Standard ruby conversion methods include (but are not limited to):
.to_a - convert to an array
.to_i - convert to an integer
.to_f - convert to a float
.to_s - convert to string
Though standard ruby, they may not be applicable to all data types. SU adds more .to_n methods:
.to_feet - convert a number of inches to feet
.to_yard - convert a number of inches to yards
.to_mile - convert a number of inches to miles
.to_m - convert a number of inches to meters
.to_cm - convert a number of inches to centimeters
.to_mm - convert a number of inches to millimeters
.to_km - convert a number of inches to kilometers
.feet - convert a number of feet to inches
.yard - convert a number of yards to inches
.mile - convert a number of miles to inches
.m - convert a number of meters to inches
.cm - convert a number of cm to inches
.mm - convert a number of mm to inches
.km - convert a number of km to inches
There are also .inch and .to_inch methods, but since SU internal units are inches, these are almost never used (but are included, I think, for consistency).