Crafting the massive copper basin that stood in the Temple required rare technological expertise, as the enormous vessel had to be cast from a single solid piece [ביאור שטיינזלץ]. The walls of this basin were a handbreadth thick [רש״י, מצודת דוד], but its upper brim gradually tapered, becoming thinner and flattened [רש״י, מצודת דוד, ביאור שטיינזלץ]. This delicate rim was styled like the edge of a drinking cup, beautifully decorated with the hammered shape of a lily flower [רוב הפרשנים].
The basin held an astonishing capacity of two thousand bat [מצודת ציון, ביאור שטיינזלץ]. A bat is a liquid measure equal to three se'ah, or roughly twenty-two to twenty-four liters [רש״י, מצודת ציון, ביאור שטיינזלץ]. In total, the basin contained six thousand se'ah of water, an immense volume equivalent to one hundred and fifty standard purification baths [רש״י, מצודת דוד]. The primary purpose of this massive pool was for the priests to wash and purify themselves. However, Jewish law requires purification in natural, gathered water rather than in a detached, man-made vessel. To resolve this issue, a channel of fresh spring water was drawn from the Etam spring, allowing living water to flow continuously through the basin [רד״ק].
A well-known discrepancy exists regarding the exact capacity of this basin, as the Book of Chronicles records its volume as three thousand bat instead of two thousand. The primary approach among commentators resolves this by distinguishing between liquid and solid measurements. The measurement of two thousand refers to liquids, which can only fill the basin up to its brim. In contrast, the measurement of three thousand refers to dry goods, which can be piled into a mound rising above the rim, adding an extra third to the total volume [רש״י, רד״ק, רלב״ג, אברבנאל, מצודת דוד].
An alternative historical perspective argues that the bat measurement always applies exclusively to liquids, and the numerical difference actually reflects changing measurement standards across generations. By the time of Ezra the Scribe, who authored the Book of Chronicles, the historical bat unit had been reduced in size by a third. Therefore, when Ezra calculated the basin's volume, he used the smaller units common in his own time, which naturally resulted in the larger figure of three thousand [מלבי״ם].