spec 
/ˈspɛk/ noun
plural specs /ˈspɛk/ noun : a detailed description of work to be done or materials to be used in a project : specification [count] — usually plural ▪ technical/design specs ▪ products that conform to specs [noncount] (US)
▪ parts built according to spec
▪ parts built according to spec
on spec 1 : without having a definite buyer or customer but with the hope or expectation of finding one when work is completed
▪ He built the house on spec. ▪ She wrote the script on spec. 2 chiefly Brit : without being sure of success but with the hope of success
▪ He wrote to the company on spec, hoping for a job.
▪ He built the house on spec. ▪ She wrote the script on spec.
▪ He wrote to the company on spec, hoping for a job.
— see also specs
