When looking at the base you will immediately notice that the base is not a traditional square.  It actually looks like someone shaved a quarter of the width off each side of the base down to the fins.  Now there are benefits and drawbacks to having the base like this.  The upshot is with a portion of the base being open to the fins, airflow is increased.  The increased airflow allows hot air to be blown off the sink faster.  Copper doesn't transfer heat into the air through convection as quickly as aluminum, so any changes made to aid this, are good.  The down side of this is the loss of some copper mass of the base.  Copper doesn't transfer heat as quickly as aluminum but it can hold more heat than aluminum (thermal capacity.)  An increased ability to hold more heat allows you more time to get rid of it.  This is the basic principle of the Swiftech sinks and why the bases of their sinks are so thick.  We will have to see if the SLK's design is a step forward or backward.

The base itself didn't have the same high luster of the fins but its finish was very nice.  No lapping needed here.

Still on the base, notice below the small feet that are included with the sink to help keep things steady.   The clip addresses this adequately in our opinion.  In addition to the feet, the heatsink included a small package of thermal goo and heaven forbid, a thermal pad.  At least it wasn't already installed!