We are really glad we got these.  Had our spa for a few days without and it was a bit tricky getting in and out.  These did the trick.  No tools needed, but it is easier to put together with two strong people as they snap together.  Also, they are designed for use with a straight or curved sided tubs, just by switching the step tops.  Once that is done, they are very secure and do not move when getting in or out due to some rubber pads on the bottom.  The grooves on the steps allow for good drainage and traction.