The UZ is also a low RG, decent flaring ball with a solid/pearl cover that has a Rough Buff finish. It is a 1/2 to a full step down in oil handling from the SZ. I have used the UZ on medium-hevay oil and just moved right. Its strength is on medium oil and it is nicely strong, in general, on true medium oil. An average drilling (given its asymmetric core) should allow the average (revs and ball speed) bowler to handle medium oil nicely. The cover is easy to adjust using any method.
--------------------
"None are so blind as those who will not see."