Pros: makes changing tips and colors easy instead of a problem
Cons: rings can be very hard to remove if you over tighten them
When I think about cake decorating, the first image that comes to mind isn't my own frazzled self, covered in flour and sugar, trying to squeeze 500 stars on a character cake.
No, I have a mental picture of a stylish pastry chef in a white smock and a chef's toque. She's a blond with her hair pulled back into a ponytail, never minding any health regulations. Her clothing and hands are squeaky clean and she sports a beautiful manicure. In her hand is a bag filled with icing and she pumps out leaves and lettering and flowers with the icing miraculously changing colors, and stiffness, all without skipping a beat.
In reality, to make leaves instead of shells, a decorator needs to change tips and a coupler is a necessity. You'd also want a coupler to use the same tip with different colors of icing (cleaning the tip between uses of course).
Without a coupler, you would need a bag and a decorating tip for each color of icing that you'd use. So, you might need 5 identical star tips to use 5 colors of frosting. If you wanted to make stars and shells in the same color, you'd still need two separate bags because once the tip is in the bag, it's pretty difficult to remove it without making a huge mess.
Obviously, if you're planning to decorate cakes, you want at least one coupler (and probably more).
What's a coupler?
Wilton come in two sizes: standard and large. Large couplers fit large decorating tips but most tips can be accommodated by standard couplers. I don't even own a large coupler which should tell you that I don't use large tips often enough to require a large coupler and I haven't found a need for one yet! The particular set covered by this category is a standard size.
The coupler consists of two parts: a base and a ring. To use the coupler, slip the base (the part that looks like a decorating tip) into either a featherweight or disposable decorating bag. Since parchment triangles are designed for a single use and for small amounts of icing, a coupler is not usually needed with them. Couplers also can be used with Wilton's Ready To Use Icing Tubes.
If this is the first time a featherweight bag is being used or you will be using a disposable bag, you'll need to cut the tip off the bag. After marking the appropriate place to cut the bag, remove the coupler base from the bag before cutting. Then, return the base to the bag.
I normally now choose the tip I'd like to use and I slip that on top of the coupler base. This means, I put the tip on the part of the base that is showing outside the bag. I had a classmate who thought that putting the tip on the coupler meant inside the bag which is why I mention this.
Now, place the ring (which looks like a big plastic ring) over the tip and screw it onto the coupler base. Don't screw it too tightly. Yes, the bag will be between the ring and the coupler base. Your bag is now ready to fill with icing.
When you need to change tips, simply unscrew the ring, pull off the old tip, replace it with the new tip and re-screw the ring into position. It's that simple.
This particular set consists of four pieces: two rings and two bases. If you need more couplers, simply buy another set. If you happen to lose a ring or a base, you can purchase those separately or you can purchase individual couplers, instead of buying two at a time.
While you don't absolutely need a coupler, they do make your life a lot easier!