I too have the 6.5 inch square and you can use it for any size smaller than 6.5 inch. I've used it for 1.5 inch HSTs and it is a necessity in my opinion.

People like this are wet blankets. I ignore quilters that think any new tool or gadget is not worth trying out and are negative without every using a new item.

I bought one for 4-1/2" HSTs, and though I used it for the whole project, I will never use it again. I much prefer Eleanor Burns triangle square up rulers. There are three different sizes. I purchased the middle size because that's what I found at JoAnn's, but may get the largest size if I need to make anything bigger than 6-1/2" square. The reason I like this one so much is because you trim before you press them open, so you only have to trim two sides. Trimming goes much faster.

I think a person should use whatever tools make the job easier for them! No you probably don't need every little tool but if you want it then go for it! There are quilt police everywhere.

I've had the boc-loc HST rulers for over a year now and, yes, they are fantastic!!! You really don't have to buy the 2.5 inch and 4.5 inch rulers. The 6.5 is the better option because it is larger, it is easier to hold down while you trim (and keep your hand out of the way). So, don't feel you need to purchase the entire 3 HST ruler set.

The flying geese rulers are very much worth the money as they trim the blocks exactly each time. I have a number of other flying geese rulers and it was a pain to have to visually line up the roof peak of my block with the lines on the ruler. Most of the flying geese rulers have thick lines so you have to be consistent with where you place the ruler over your block to trim. Also, I found that my Eleanor Burns flying geese rulers were not accurately cut and 2 of the 3 from the set I purchased several years ago were almost 1/8 inch short. I ended up with a bunch of flying geese that were 2 1/2 by 4 3/8 inches.

You are right that you can use one size to make many different size blocks--at the time I bought mine I wasn't aware of how versatile they would be. Once I receive the 9.5 HST I will be set for good. I am doing an off center log cabin with flying geese blocks in the right upper corner--I'm using both the flying geese ruler and the 4.5 HST. Believe me, it makes it much easier!