Lucky_P, I always thought the progesterone was in a dehydrated gel form and in those grooves on either side of the CIDR! Am I understanding correctly that it is in fact impregnated into the plastic of the CIDR?
I have always thrown them away as I thought the progesterone would wash off, and figured that wasting a dose of semen, usually more expensive than a CIDR unless collected from your own bull, by being a scrooge on the cost of the CIDR, was economically stupid!