yep, no base plates; the foam is very strong, yet very plyable (sp?) so it will just stretch over most any width opening of stacks. They are mostly used by guys using EFI with DCOE stacks, but they will fit most everything and if not, you just carve them up a bit wider with a scissor
My stacks are 40mm high btw and I made two small extra holes (yes, with the scissors) for the tops on the emulsion tubes with the air correction jets.
Good luck,
Walter