Probably a foolhardy quest, but does anybody know which modern maker the 156 crook is most similar to, or of a tech who could make one if they had an original? The one I have has some red rot in the crook and will need to be replaced.

Bach 42/50 is essentially identical - OD, span, similar bending radius

<LINK_TEXT text="https://www.mkdrawing.com/product/tromb ... low-brass/">https://www.mkdrawing.com/product/trombone-bach-oem-replacement-42-42b-and-50b-yellow-brass/</LINK_TEXT>

I have a (approx. 1979-1980) Holton 256, which should be the same model except the 256 has the screw bell rim. The crook on my slide is very wide, about 1/4 inch wider than the Bach 42/50 crook. However, I believe the bore is slightly smaller than the Bach 42/50. I would estimate that the Holton 156/256 slide crook would be about .595 or .596 inch.

I doubt that you will be able to find a crook that you could simply plug into place and solder, unless you have one that is expertly made. A Bach 42/50 crook would probably work well but you would need to have all of the braces adjusted to match the width of the new crook.

[quote="Crazy4Tbone86"]The crook on my slide is very wide, about 1/4 inch wider than the Bach 42/50 crook.[/quote]

I've had two 156s and a 159 from various decades and they were all 50-span. Your 256 seems like an outlier... Holton gonna Holton

<LINK_TEXT text="viewtopic.php?p=136117#p136117">https://trombonechat.com/viewtopic.php?p=136117#p136117</LINK_TEXT>

[quote="Crazy4Tbone86"]I doubt that you will be able to find a crook that you could simply plug into place and solder, unless you have one that is expertly made. A Bach 42/50 crook would probably work well but you would need to have all of the braces adjusted to match the width of the new crook.[/quote]

Safest to assume the need to parallel everything after any crook replacement, even if OEM.