Does usury apply to manufactured items that are not typically weighed or measured?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
For manufactured items such as processed iron, lead, copper, cotton, flax, wool, and silk, the explicit ruling attributed to Ahmad regarding garments and cloaks is that usury does not apply; he stated there is no harm in exchanging one garment for two garments. This is the view of the majority of scholars. Similarly, exchanging one coin for two coins, one knife for two knives, or one needle for two needles is not subject to usury, as their basis is weight. The correct position is that usury does not apply to any of these items because the operative cause (weight or measure) is absent, and there is no explicit text or consensus establishing usury for them.
Supporting text
A second opinion, chosen by Ibn Aqil, holds that usury applies to all these manufactured items because their original substance was weighed, and the process of manufacturing does not remove them from that category, similar to bread. The القاضي (Al-Qadi) suggested that if the item's weight is intended after fabrication, such as basins, then usury applies, but not otherwise.