You are going to have a lot of weight on them those nobs will be hard to turn. Look at some with a ratcheting lever on them like Foot Master.
Foot Master Leveling Caster, Ratchet, 63 mm Nylon Wheel, 1/2-13 Stem, Swivel, 500 kg Cap, NBR Foot Pad, Black GDR-80-S-NYN-FBL-1/2 | Zoro
Order Foot Master Leveling Caster, Ratchet, 63 mm Nylon Wheel, 1/2-13 Stem, Swivel, 500 kg Cap, NBR Foot Pad, Black, GDR-80-S-NYN-FBL-1/2 at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.
www.zoro.com