The complete diameter of the "Toonie" is 28 mm, the outer ring is 99% nickel and the inner coin is 92% copper, 6% aluminum, and 2% nickel.
They have minted these since 1996, so there are millions in circulation.
"Many Toonies in the first shipment of the coins were considered defective, because they could separate if struck hard or frozen, as the centre piece would shrink more than the outside. This problem quickly garnered media attention and eventually was believed to have been corrected, and the initial wave of so-called Toonie popping blew over a few months after the coin's introduction. Although the public appears to believe the Toonies were corrected, the coins can still be separated if struck hard or frozen. Such a separated coin may still be redeemed at a bank for its face value; however, Canada's Currency Act explicitly reads "No person shall ... melt down, break up or use otherwise than as currency any coin that is current and legal tender in Canada."[3] Punishment is a fine of up to $5000.00 and/or up to 5 years."