This is a tube holder adaptor for a cold block. It has a 2mm top layer thickness and each hole has a diameter of about 3mm and shrinks down to 2.8 mm. It'll slide on top of the cold block and stay in place while firmly holding the tubes in place. This was done per request by biology professor Chrissy McAllister at Principia College. 

Given that this is 3D printed and can be modified, it meant that the professor didn't have to buy a new cold block, which would have cost her upwards of $100. Instead, this was less than $1 worth of filament (not including time for designing it).