I found it a bit hard to grip the implement height stop thumbscrew on my new L3301HST tightly enough to crank it down enough to keep the stop from moving when I bump it with the height lever. The thumbscrew is just an ordinary M6 x 1mm pitch thumbscrew, 20mm long. I replaced it with a lever cam screw from McMaster-Carr for around $12.50, making the stop easier to adjust. The part I used is part number 5720K31. There's also an all stainless steel version for around $42, but that's a bit more deluxe than I need. Here are the before and after pictures: