I use a home brew one at each end of the feedline as I wanted to ensure that the feedline did not act as a BOG. I used 4 each of these to wrap 6 or 7 turns of the coax.

https://www.mouser.com/ProductDetail/623-2631803802

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Gary Mitchelson
NC3Z/4 Pamlico County, NC FM15
NC AHIMT COML
SHARES NCS997