[15.7" (40 cm)] I had the travel Benro tripod but didn't think that I would need the 23.6 go rail until I started shooting Macro. It has been a pleasure using it for overhead shots with food photography too. So glad that I purchased it.

[18 x 2.5 x 2.4"] I own a Benro 2 series tripod that came with a video head. I wanted a bullhead but did not feel like lugging an entire other tripod around. I figured if I purchased this column, I could put the bullhead on it then just change out the center column as my needs require. It has worked very well. I can change the two posts in less than one minute and am pleased with the quality and compatibility of this center column. For short money, it's a great way to get one tripod to work twice as hard. My gear is all about versatility and this matches up with my desire to get as much utility as possible out of every dollar.

[0.65 lb] Purchased to go with the video head to get a little more height if needed. Goes perfect with a Benro FGP28A Go Plus 4-Section Aluminum Travel Tripod.

[18 x 2.5 x 2.4"] A month ago, I purchased a used Induro A313 tripod from eBay. The good news is that the tripod was at a reasonable price and in great shape. However, it did not come with a center column. I thought I was soo smart; I figured the spare Induro column I had would work. Nope! Too small. I should have researched the different series designs of older Induro tripods.
So, to get the tripod usable, I purchased, on a chance, that it would work, a Benro AC3 Aluminum Center Column for 3 Series Tripods. Yeah! It fits and works; it locks when tightened, but the channel on the column does not engage with the peg that holds the bushing from turning. However, not an issue, the tripod is now usable; B&H to the rescue.
Thanks for letting me share my story.

[15.7" (40 cm)] The Benro AC2 center column is a 100% perfect fit in the Gitzo Reporter (Series 2, 28mm) column assembly. My Reporter has a Tilt/Roll type head. This is very clumsy for leveling a panning base so I wanted to replace it with my Sirui K40-X ball head. This requires a replacement Rapid-style center column with a 3/8-16 thread. The 57mm AC2 platform diameter is slightly smaller than the 68mm base of the K40-X. This is not a problem as the platform is very sturdy and the ball head is firmly mounted. There is no wobble or instability. The 3/8-16 thread on the AC2 column mates with the ball head without needing an adapter bushing. Install the column by unscrewing the bottom hanging bracket, drop in the column, then reattach the hanging bracket. Other than being a black anodized finish, this AC2 column is a perfect match. I can quickly adjust the ball head platform to level, install my panning base and go. Highly recommended.

[18 x 2.5 x 2.4"] My Sirui T-1205X tripod's central column brokeaccidentally. Sirui doesn't sell these columns separately. I ordered this one. And I found it fully compatible with my Sirui! It has the same diameter 2.4 cm.Yes, it's made of aluminium unlike my broken one, and it's a little higher, but it's doesn't matter for me. Thanks to Benro and thanks to BH!

[18 x 2.5 x 2.4"] High quality build and excellent fit on my tripod. Holds my camera with out any wiggle in all positions.

[0.65 lb] My AT-213 (alloy) tripod came with a plastic bushing to take up the eighth of an inch space in the center of the tripod. It broke while lowering the tube. I assumed this bushing would come with this new tube, after speaking with Induro,it did not. The used AT-213 (aluminum) tripod I purchased from B+H,fit this tube perfectly. Induro supplied the bushing at N/C,and I returned this tube to B+H. Rather odd both of these tripods did not have the same center diameter.