48 C.F.R. § 9904.407-50
(a)
(4) A labor-rate standard may be set to cover a group of direct labor workers who perform disparate functions only under either one of the following conditions:
(b)
(2) Where material-price standards are used and related variances are recognized at the time purchases of material are entered into the books of account, they shall be accumulated separately by homogeneous groupings of material. Examples of homogeneous groupings of material are:
(3) Where material-price variances are recognized at the time purchases of material are entered into the books of account, variances of each homogeneous grouping of material shall be allocated (except as provided in paragraph (b)(4) of this subsection), at least annually, to items in purchased-items inventory and to production units receiving items from that homogeneous grouping of material, in accordance with either one of the following practices, which shall be consistently followed:
(d) A contractor's established practice with respect to the disposition of variances accumulated by production unit shall be in accordance with one of the following subparagraphs: