PP. 8 connected 0.2 ml tubes. Separate, domed or flat caps are available in strips of 8. They are easy to open and close without tools. The tubes have a holding strap at one end, and the cover strips on each cap have a small lip on the side for careful, contaminationfree opening. PP. 8 connected 0.2 ml tubes. Separate, domed or flat caps are available in strips of 8. They are easy to open and close without tools. The tubes have a holding strap at one end, and the cover strips on each cap have a small lip on the side for careful, contaminationfree opening.