THETA THS921A HV Micro Coreless Servo

Excuse my ignorance but what exactly are “coreless” vs a standard servo? I don’t mean speed specs as in “they may be faster” but what is the engineering, mechanical differences? I love and trust Helidirect but I’m at a loss here via this question. Thanks in advance guys.

Awesome little servo, very fast

Great little servo. Great service from HeliDirect .

Awesome product…good price!!!

If u don't buy these rn now then F U!
Also I might of heard brushless micros might be in the works?

Excellent servo. It will be used for engine accelerator. Very reliable and 8.4V

Very powerful I use my 3d 48" foamy for extreme Flight

This is a solid, reliable servo that has served me well for a number of months. I don't have any gripes with the servo itself but with the Theta accessories. First, the included servo horns are pathetically flimsy and are very easy to snap during something as benign as a hard landing. With a couple pennies more, they could have included the thicker aftermarket Theta-branded servo horns. Also, the Theta programming box was poorly executed and a waste of money. Hopefully you won't need to purchase one, but if you need to adjust this servo in any way, prepare to be frustrated.