I just searched for your filter, a Sta-Rite posi-flo.
Original equipment cartridge calls for WC 108-58S2X. Correct? Should be 8-11/16 OD, 25-11/16 tall. The openings should be 4-11/16 ID, and the top should have 12 concentric slots.
Unicel listing is UHD SR100.
Did Leslies match up the new to the old? I assume house brand on the replacement.
I know it could be a pain in the behind to remove the cart. If you do, check the dimensions as listed from Sta-Rite. If the top or bottom openings are even the slightest too large, pool water will bypass. The filter should fit very snug on the mount points, where it needs just a little force to install.