Reasonable RCA Connectors?

Copper is silver plated 
Silver is solid silver conductors
Pure is a higher quality solid pure silver 

What is a difference in sound?

None of the conductors on KLEI RCAs are solid silver.

https://forum.audiogon.com/discussions/kle-innovations-silver-harmonyrca-s-not-silver-eh

From the distributor - Parts Connextion

Copper Harmony - ”Copper" Harmony Phono RCA Plug (Hard Silver-Plated - both Ground & Signal)”

“Silver" Harmony Phono RCA Plug (Pure Silver Ground - Silver-Plated Copper Signal)

”Pure" Harmony Phono RCA Plug (Pure Silver Ground & Signal)”

Absolute" Harmony Phono RCA Plug Highest Grade - Pure Silver on both Ground and Signal” 

The mystery continues. PC uses quotes in the description suggesting it came from the manufacturer at some point.  

@grannyring - Parts Connecxion is one of the distributors that continue to post mis-information about KLEI products on their site

KLEI has asked them (and others) to correct their information many times, but for some reason they will not comply

@Maxima95 is indeed correct - they are all silver coated copper.

The "magic" is in the design of the pins and the thickness of the silver coating and purity of both silver and copper used on both the centre pin and the neutral.

That "formula" is a closely guarded KLEI secret. 

The fact that they are silver coated does not make them any LESS special. 

I have reviewed their four original Harmony RCA's at length, spending dozens of hours evaluating the performance of each plug as it compares to the next in the lineup, and found each model to provide progressively better sound quality, culminating in the Absolute Harmony - their flagship model.  

I use the Absolute Harmony on all of my cables - whether Analogue or SPDIF cables and they are the best I have used to date.

The link posted above goes into great detail about various aspects of these RCA's

Bottom line - they are exceptional RCA's

Regards - Steve