Any nozzle will let a foam solution pass through. The nozzle selection will determine what kind of finished foam product is provided and the stream reach. No one nozzle can be the best at every incident.

Foam Tube/Branchpipe
When using an eductor system, an air aspirating nozzle uses the venturi effect to draw air into the tube. The nozzle is designed to agitate the foam solution by some type of constriction or screen, mix with air and produce the finished foam product before it exits the nozzle. The firefighter operating the nozzle should take care not to block air intakes or the finished product will be of lower quality (less bubbles). This type of nozzle is typically best for application on flammable liquids. The model we have is an Angus F-450 - Foam Branchpipe (Engine 63) which produces a variety of foam application rates as described in the foam/eductor matching table. The only downfall is that if not preconnected, setup time will be increased. This nozzle should not be used with CAFS, it will destroy bubble structure.

Bubble Cups 
All of our Bubble Cup models have been taken out of service
A bubble cup nozzle has no internal air entrainment, only turbulence/agitation by small teeth inside the extended tube. The Bubblecup (TFT) relies on mixing foam solution with air while the stream is on its way through the bumper. It provides a slightly better finished foam product than a fog nozzle with a greatly diminished reach.
It is very important to note that these models do not operate like our Elkhart SM-20 or SM-30 nozzles which can maintain gpm through fog or straight stream. Turning the cup all the way left will change the flow from 95gpm to 20gpm. While this nozzle can deliver AFFF and produce the needed film layer in straight stream mode, turning the cup left will improve foam bubbles but reduce the application rate (down to 20gpm!) and reduce stream reach.

Foam Tube/Aeration Attachments
Attachment foam tubes can be clamped/fixed onto combination nozzles if the tube is specifically designed for the nozzle. The process uses teeth from the fog nozzle, air entrainment from the intakes, agitation when solution passes through a screen like device and the foam tube to produce the finished foam product. Such a device is the next best to a branchpipe in finished foam product quality. Two more advantage are that the device can be quickly attached to existing combination nozzles and they are generally only limited to the capability of application rate of the nozzle/eductor combo.

Combination Nozzles
These can use foam solution and produce a lower grade finished foam product. Mechanical agitation occurs somewhat in the nozzleand at the teeth but would mostly require the streams to be "splattered" onto the ground or other surface. These conditions can also set up more of a chance for fuel disturbance. Air entrainment is minimal and also causes the decrease in foam quality. The finished foam with AFFF will still produce a film layer but without the higher quality insulation/bubble structure of foam tube attachments or branchpipes. Nozzles will already be attached to crosslays and would not require a time delay in setup or can have a foam tube or aeration attachment placed on them.

Solid/Smooth Bore Nozzles
When using an eductor system, solid bore nozzles do not have the capability to create hardly any type of foam production although they can still deliver AFFF for a film layer. The only way a solid bore nozzle can create any kind of low quality finished foam is to bounce the stream off of the ground or other objects for agitation. "Bouncing" a stream off of a flammable liquids surface is not an option since it will disturb the film layer or splash the flammable material creating more available surface area and creating larger fire volume. This weakness with eductor systems is offset when using CAFS.
With a CAFS (E62), air is entrained with solution before leaving the discharge and mechanical agitation occurs in the hoseline. Finished foam is delivered to the nozzle and the solid bore maintains bubble structure and will be the best selection (with CAFS).