These are high-quality Stainless Steel Quick Release wheelchair axles.  They have a large silver button.

Specifications: 

Length: 5" long (4.95" - 5.2")
Axle Size: 1/2"
Material: Stainless Steel
Button Size: Large
Button Color: Silver

Used on the following wheelchair bands with 8mm (5/16”) Front Caster Axles: 

1. Can be used with Top End sports chairs with 2.5 (longer) Reciever but you will need a 1/2" spacer