Couple of things to consider leg levelers
for your bench

1. you want some friction at the contact
area where the leveler meats the floor.
The ones I used are 3 " in diameter

2. you want the foot to swivel so it'll
sit flat on the floor

3. the easier they are to adjust the more
apt you are to relevel as things settle.
The ones I used are adjustable from
the top using an allen wrench - much
easier than trying to get two wrenches
under a leg/base

I don't know what the bench you're doing
look likes. The leve levelers I used work
great on a sled base - won't work on four
leg bench though. I also don't know if
this is the first of several benches you
intend to make. Most folks start out with
a quick and dirty bench which later becomes
an assembly bench and then build a
better, more useful one later. Some go
through several "ideal benches" before
settling on their "final bench".

Before I built Das Bench I went through
Scott Landis and Allen's workbench books
along with all the magazine articles I
could find on benches and bench building.
Asked questions here and from a few
woodworkers I know.

As strongly recomended, I bought the
hardware (vises) before working out
the first of many iterations of scaled
"plans".

Enjoy building your bench, you'll learn
a lot.

charlie b