Grant-bio PTR-25 Mini Rotator Lab Tube Mixer With PRS-22 Holder and Power Supply 155505078472 knob is hard to pull

knob is hard to pull out

Here's a brief description of the features and specifications of the SMC MKB63TF-10LZ cylinder:

Manufacturer PNY Model Number VCQM6000-T SKU 19-76996 Ref 23-110977

5cm Aux Wide Angle Lens for f/2

Grant-bio PTR-25 Mini Rotator Lab Tube Mixer With PRS-22 Holder and Power Supply 155505078472 knob is hard to pullCondition Used Description This item is fully tested and in excellent working order. Item will come with a 30 Day Warranty. Cosmetically in good condition showing minor scuffs scratches blemishes from previous use. Includes Mini Rotator Lab Tube Mixer, PRS 22 Holder, and Power Supply as pictured. No additional items or accessories are included. Pictures are of one of the actual units available. Inventory is on hand and ready to ship. Please feel free