Grant, this is what Andy sent me for size: 6.35mm to 8mm couplers and solid ones. My old ones are 25mm in length and 20mm in diameter. I can find many with the correct hole sizes and 25mm in length. But the diameter varies. The ones I ordered are 14mm in diameter but solid so I’m hoping solid enough. I looked at the ones on Amazon like the V2 versions but they seem to have a rubber cushion of some sort. I don’t see how they would be any better as they will flex. I like the solid ones as they seem to have bigger set screws with 4 screws per coupler. I ended up ordering off of Ebay because the shipping times for Amazon were way out. Like late April, May and even June. I ordered from a US supplier last night and they are already shipped and due April 2. The were $8/pair (USD) so had to order quantity 2. Will have one extra if needed. Here is link - https://www.ebay.com/itm/2-pcs-Aluminum-Blue-Shaft-Coupling-Rigid-Coupler-Motor-Connector-CNC-DIY/353020805184?ssPageName=STRK%3AMEBIDX%3AIT&var=622229448895&_trksid=p2060353.m2749.l2649
Oh! And free shipping.