Definatly urethane. I had 4 of the blue ones including one that was a boo-boo from Columbia and had a 2 piece weight block in it
Castaway's Bowlers Pro Shop
Calumet City,Il. 60409
(708) 862-1602
Arsenal: Aftermath, Bank, Break Point Pearl,Sideways x2,Profit x2, Clutch Pearl,Maniac x2,Lunatic,Heist Pearl,Link,Hype urethane,Epicenter, Desperado,Mars, Grenade Pearl,T-Zone
http://s485.photobucket.com/albums/rr220/stormed1/My%20Arsenal/Bowlingboards.com