Kreg started off with a two hole all aluminum jig,it was the first one I bought and mounted on my bench.It was a one piece item...then they came out next with the same jig only it was air driven,you installed the wood in the jig stood on a pedal it forced the ram forward to holed the work piece and you drilled your holes,released the pedal and your work piece is freed to remove.You never have to release your hand from your work or drill.Next they came out with a package deal ,clamp ..plastic jig...drill with collet..adjustable jig for differant sizes of wood thicknesses and different sizes of screws.Then they also came out with a single portable jig for you pocket...thats the last one I bought because it came with another collet and drill bit .It`s cost was the same as a replaceable drill bit,I couldn`t pass that one up....If you drill as many holes as I have....well I broke two bits so far and worn out 2 more....So a kit coming with a drill bit and collet was a no brainer for me.Thats why I have four units now...Which one is best?? Well if your at home workshop has an air compressor you can`t beat that one,but on the road the first alum. one I bought goes into my vice and away I go...but for different sizes of wood The plastic adjustable is the one I reach for,it travels well too in its on case.
The single hole plastic is the only one I never had a use for yet...I really bought it for the bit.
