Related על ראש השנה 3:6

If a horn was long and he shortened it, then it is fit. If he has scraped it inside or outside, it is good. Ha [a]he disguises it inside, it is useless ; [if he] has it [covered up] on the outside, then it is fit for purpose. Did [a]he disguise the mouthpiece or did he extended, even if [it happened] with [material] of the same kind, it is invalid. If it was punctured, and if [a]er [then] stopped it, even if [it was done] with [material] of the same kind, it is unsuitable if it prevents blowing; but if not, it is fit. If he has put two horns together and blown them, then when he has heard the sound of the inner one, he has done his duty; if he has heard the sound of the outside, then he has not fulfilled his duty. The size of the horn: that [d]er [bloa-ser] take it with his hand and blow kana