There were several versions of the Zeiss 80mm Planar for the Hasselblad 500 series: C, CF, CB, CFI, CFE. All of them (as well as other Zeiss lenses) had a bayonet-style mount on the front of the lens for the filter. Depending on which Zeiss 80mm Planar you have, it might have either a 50mm or 60mm bayonet mount, a.k.a., Bayonet-50 or Bayonet-60.

The original Zeiss 80mm Planar for Hasselblad (the C lens) used the Bayonet-50 filter mount. The other Planar 80mm lenses for Hasselblad use the Bayonet-60 filter mount.

Chances are, you probably have a lens with a Bayonet-60 mount. To be certain, check your lens against the Zeiss Lens Datasheets page at hasselbladhistorical.eu.

You have a few options to mount your Lee system, and other screw-on filters if you would like to use them:

1. The Lee Bay 60 Adapter Ring for Foundation Kit is the most direct route to mount your Lee filter holder, but still leaves you unable to mount your 72mm IR filter. Mount the Bay60 adapter on the lens, and snap the Lee square holder onto the adapter. About $60 USD.

2. A Bay60-to-67mm threaded adapter ring can be had for under $10 USD. From there, a 67mm-to-72mm step-up ring will allow you mount your IR filter or your 72mm Lee adapter.

   Because the Bay60-to-67mm adapter uses the inner bayonet lugs on the front of the lens, the outer bayonet lugs are still available to use with the Bayonet 60 mount lens hoods, if you are using one of those. Many of those hoods have room inside to still mount a 67mm filter, such as a polarizer, if necessary.

3. Bay60-to-72mm threaded adapters are available, but they seem much less common, and seem to command a higher average price.

The possible problem with stacking adapters (and filters) is that, depending on the angle of view of the lens, you might be vignetting issues. If you are planning on mounting both the IR filter and your Lee system, I'd suggest getting a Bay60-to-72mm threaded adapter. This will cause less potential vignetting than getting a Bay60-to-67mm threaded adapter + 67mm-to-72mm step-up ring, and then mounting your IR filter and 72mm Lee adapter.

However, if you have other, wider angle lenses for your Hasselblad that you'd like to use filters with, you might consider returning your 72mm IR filter and Lee 72mm adapter, and choose a larger filter diameter to standardize on, such as 77mm.